Without a doubt, free porn is the Eldorado of being online. That being said it is nice to support those who produce the lacy stuff, but why drain your canteen money? Save a few quid while you wank.
To make this list a site should be: 1. Free of membership requirements. 2. Contain no gimmicks. 3. Have sufficient discounts that cover the upper echelon of sites, as well as those lesser known.