Good exercise site?

Anyone know of a good exercise site that has videos and such? I am looking for one where I can type in what my goal is (back rehab) and it shows the exercises and videos, or if anyone can recommend some good sources on rehabing the lower back that would be great also( I have tried the super joints, relax into stretch, yoga, etc...). I was diagnosed by one doctor with Ankalosing Spondalitits(sp?), another one diagnosed me with Scoliosis and a thrid one said I just had weak backmsucles and that the second one's X-Ray didn't count because I was in a spasm when it was taken. The third one brought in a another doctor who said there didn't seem to be any arthritis. I really need something to fix up my back, it is o.k. most of the time but I can't train when it goes. Thanks, Jason

Sweet thanks, thats kind of what I was looking for.