Personally, I love this site: http://www.posemaniacs.com/

If you're looking for a pose in particular, it can take a while to find, but when you do you get a nice turnaround for your efforts.
I was a bit iffy about the muscles and such, but they do help you with anatomy as well :3

Enjoy <3

Oh god pose maniacs xD
I use that site whenever i could but i can't find the search section now and hell there's a shit ton of usefulposes

All I can offer is besides posemaniacs is DeviantArt under the category Resources & Stock Images >Stock Images >Model and then continue to pick a specific model and/or type in keywords to help narrow down what you're actually looking for and browse away! xD It's super helpful if what you are looking for is not on posemaniacs (I use both a lot) the model stocks on DA offer way more poses, but none of them may be what you are looking for, this has happened to me many times and I have had to slightly change my idea to find one that fits xD Hope this helps!! ^^

Haha yeah stock images on deviantart are better but limited in a way sometmes. But thank you for the suggestionn

Sometimes when I can't find what I need I take a picture of myself and use that as a reference xD looking in a fullbody mirror does wonders -w-