I like AdultFolio, treats grown-ups like grown-ups. I've booked a couple of models through the site, been a good experience, I think if you can show you've experience of working to adult levels then the models do take you seriously. I think the administrators do a good job of running things, and personally I've not experienced any problems. I very rarely interact on the forums, though some good issues are raised and there is good advice to be found too. All in all the site allows me to post examples of my work, meet and interact with new models. As I say it's the general non judgemental atmosphere that appeals, although it appears miscreants are dealt with quite quickly, which makes the site as far as the administrators are able a safe space for all concerned.

I find both inspiration and models on Adultfolio. Very helpful to find reviews that help to create productive collaborations.