For insiration I spend a decent amount of time on 500px. There are some very talented people from all over the world on that site.
https://500px.com/
Has for gaining more knowledge some free sites are Wetpixel http://wetpixel.com/ and Divephotoguide http://www.divephotoguide.com/ for underwater stuff and on land I've used a ton of differnet sites - Strobist http://strobist.blogspot.ca/ , Petapixel https://petapixel.com/ and on Youtube I use phlearn https://phlearn.com/

Hope this helps, happy shooting.