If you're into bondage, teasing and deep submission - and willing to pay a few bucks - I can recommend the kink.com sites: hogtied, whippedass and the rest offer great shoots with convincing, sexy Dominants and lovely submissives who endure amazing things. And the submissive(s) also talk about what it felt like at the end of each shoot, which is a very interesting feature. I admit their prioductions are not non-stop no-holds barred, heavily sadistic stuff where the models would seem totally to fear for their lives, the emphasis some of the time is more on the teasing interplay and roasting of the sub, who nevertheless gets tried hard, but it's very good, great production qualities and with people who really believe in what they do.

For free videos - well, youtied.com has both amateur vids and previews and shorts from some commercial sites, but most of them aren't too heavy. Soem are very hot, though.