YouTube banned Two Knotty Boys for their videos, which frankly surpised me given what I have seen on their site. This is kind of disturbing given that there was no nudity, infact their modles all used full body stockings. But they have managed to return with a few videos at under the name TyingItAllTogether. It is purely vanillia but they have some good knot tying techniques, so you might want to check some out. Here is one of how to tie a knot for suspension:
They do provide links to some of their older stuff, so check them out too.