daydreaming during the lecture? Was the lecture too complex to digest in one sitting? Missed a class due to sickness? No problem, listen to the recorded lectures over and over again as you like. What's even amazing is that, class discussions are recorded. You can even download the script of both lectures and class discussions! Some sites even offer lifetime access to the course materials including future updates.

There has been an explosion in the number of elearning sites in recent years. Below is not a complete list, but a decent one to start with.

"Education is the most powerful weapon which you can use to change the world"

MIT OpenCourseWare - is the project that started the OCW / Open Education Consortium [http://www.oeconsortium.org], launching in 2002 with the full content of 50 real MIT courses available online, and later including most of the MIT course curriculum — all for free — with hundreds of higher ed institutions joining in with their own OCW course materials later.

Coursera - is a learning site offering courses (free for audit) from over 100 partners — top universities from over 20 countries, as well as non-university partners — with verified certificates as a paid option, plus specializations, which group related courses together in a recommended sequence.

edX - The site offers free subject matter from top universities, colleges and schools from around the world, including MIT and Harvard. Many courses are “verified,” offering a certificate of completion for a nominal minimum fee.

Audacity offers courses with paid certification and nanodegrees — with emphasis on skills desired by tech companies in Silicon Valley — mostly based on a monthly subscription, with access to course materials (print, videos) available for free.

Udemy hosts mostly paid video tutorials in a wide range of general topics including personal development, design, marketing, lifestyle, photography, software, health, music, language, and more.

Khan Academy - is one of the early online learning sites, offering free learning resources for all ages on many subjects, and free tools for teachers and parents to monitor progress and coach students.

Harvard Extension School - Harvard’s OLI (Open Learning Initiative) offers a selection of free video courses (taken from the edX selection) for the general public that covers a range of typical college topics, includings, Arts, History, Math, Statistics, Computer Science, and more. The Canvas Network offers mostly free online courses source from numerous colleges and universities, with instructor-led video and text content, certificate and degree options for select programs.

Stanford Online is a collection of free courses billed as “for anyone, anywhere, anytime” and which includes a wide array of topics that include human rights, language, writing, economics, statistics, physics, engineering, software, chemistry, and more.

Stanford Online Continuing Studies – Another one from Stanford. Most of the courses offered are post graduate for a fee.

Codecademy offers data science and software programming (mostly Web-related) courses for various ages groups, with an in-browser coding console for some offerings.

Stanford Engineering Everywhere houses engineering (software and otherwise) classes that are free to students and educators, with materials that include course syllabi, lecture videos, homework, exams and more.

Big Data University covers Big Data analysis and data science via free and paid courses developed by teachers and professionals.

Better Explained offers a big-picture-first approach to learning mathematics — often with visual explanations — whether for high school algebra or college-level calculus, statistics and other related topics.

HOW Design University (How U) offers free and paid online lessons on graphic and interactive design, and has opportunities for those who would like to teach.

HTML Dog is specifically focused on Web development tutorials for HTML, CSS and JavaScript coding skills.

Skillcrush offers professional web design and development courses aimed at one who is interested in the field, regardless of their background — with short, easy-to-consume modules and a 3-month Career Blueprints to help students focus on their career priorities.

Hack Design with the help of several dozen designers around the world, has put together a lesson plan of 50 units (each with one or more articles and/or videos) on design for Web, mobile apps and more by curating multiple valuable sources (blogs, books, games, videos, and tutorials) — all free of charge.

Scratch – Imagine, Program, Share from MIT is a causal creative learning site for children, which has projects that range from the solar system to paper planes to music synths and more.

E-learning for kids offers elementary school courses for children ages 5-12 that cover curriculum topic including math, science, computer, environment, health, language, life skills and others.

Ed2go aims their “affordable” online learning courses at adults, and partners with over 2,100 colleges and universities to offer this virtual but instructor-led training in multiple categories — with options for instructors who would like to participate.

GCF Learn Free is a project of Goodwill Community Foundation and Goodwill Industries, targeting anyone look for modern skills, offering over 1,000 lessons and 125 tutorials available online at anytime, covering technology, computer software, reading, math, work and career and more.

Stack Exchange is one of several dozen Q+A sites covering multiple topics, including Stack Overflow, which is related to computer technology. Ask a targeted question, get answers from professional and enthusiast peers to improve what you already know about a topic.

HippoCampus combines free video collections on 13 middle school through college subjects from NROC Project, STEMbite, Khan Academy, NM State Learning Games Lab and more, with free accounts for teachers.

Howcast hosts casual video tutorials covering general topics on lifestyle, crafts, cooking, entertainment and more.

Memrise — Lessons on the Memrise (sounds like “memorize”) site include languages and other topics, and are presented on the principle that knowledge can be learned with gamification techniques, which reinforce concepts.

SchoolTube is a video sharing platform for K-12 students and their educators, with registered users representing over 50,000 schools and a site offering of over half a million videos.

Instructables is a hybrid learning site, offering free online text and video how-to instructions for mostly physical DIY (do-it-yourself) projects that cover various hands-on crafts, technology, recipes, game play accessories and more. (Costs lie in project materials only.)

creativeLIVE has an interesting approach to workshops on creative and lifestyle topics (photography, art, music, design, people skills, entreprenurship, etc.), with live access typically offered free and on-demand access requiring purchase.

Do It Yourself (DIY) focuses on how-tos primarily for home improvement, with the occasional tips on lifestyle and crafts topics.

Adafruit Learning System — If you’re hooked by the Maker movement and want to learn how to make Arduino-based electronic gadgets, check out the free tutorials at Adafruit Learn site — and buy the necessary electronics kits and supplies from the main site.

Grovo — If you need to learn how to efficiently use a variety of Web applications for work, Grovo has paid (subscription, with free intros) video tutorials on best practices for hundreds of Web sites.

Open Yale Courses (OYC) are free, open access, non-credit introductory courses recorded in Yale College’s classroom and available online in a number of digital formats.

Open Learning Initiative — Carnegie Mellon University’s (CMU’s) Open Learning Initiative (OLI) is course content (many open and free) intended for both students who want to learn and teachers/ institutions requiring teaching materials.

MIT Video offers over 12,000 talks/ lecture videos in over 100 channels that include math, architecture and planning, arts, chemistry, biological engineering, robotics, humanities and social sciences, physics and more.

Quantum Physics Made Relatively Simple is, as the name implies, a set of just three lectures (plus intro) very specifically about Quantum Physics, form three presentations given by theoretical physicist Hans Bethe.

Open UW is the umbrella initiative of several free online learning projects from the University of Washington, offered by their UW Online division, and including Coursera, edX and other channels.

UC San Diego Podcast Lectures — Podcast USCD, from UC San Diego, is a collection of audio and/or video podcasts of multi-subject university course lectures — some freely available, other only accessible by registered students.

University of the People offers tuition-free online courses, with relatively small fees required only for certified degree programs (exam and processing fees).

NovoEd claims a range of mostly free “courses from thought leaders and distinguished professors from top universities,” and makes it possible for today’s participants to be tomorrow’s mentors in future courses.

Apple Developer Site — Apple Developer Center may be very specific in topics for lessons, but it’s a free source of documentation and tutorials for software developers who want to develop apps for iOS Mobile, Mac OS X desktop, and Safari Web apps.

Google Code — As with Apple Developer Center, Google Code is topic-narrow but a good source of documentation and tutorials for Android app development.

Code.org is the home of the “Hour of Code” campaign, which is aimed at teachers and educators as well as students of all ages (4-104) who want to teach or learn, respectively, computer programming and do not know where to start.

Mozilla Developer Network (MDN) offers learning resources — including links to offsite guides — and tutorials for Web development in HTML, CSS and JavaScript — whether you’re a beginner or an expert, and even if you’re not using Mozilla’s Firefox Web browser.

Learnable by Sitepoint offers paid subscription access to an ebook library of content for computers and tablets, and nearly 5,000 videos lessons (and associated code samples) covering software-related topics – with quizzes and certification available.

Pluralsight (previously PeepCode) offers paid tech and creative training content (over 3,700 courses and 130K video clips) for individuals, businesses and institutions that covers IT admin, programming, Web development, data visualization — as well as game design, 3D animation, and video editing through a partnership with Digital-Tutors.com, and additional software coding lessons through Codeschool.com.

CodeHS — CodeSchool offers software coding lessons (by subscription) for individuals who want to learn at home, or for students learning in a high school teacher-led class.

Aquent Gymnasium offers a small but thorough set of free Web-related lesson plans for coding, design and user experience, but filters access by assessing the current knowledge of an enrollee and allows those with scores of at least 70% to continue.