I know I could probably research this, but with all the marketing hype, it'd probably be easier to just ask.

Canon Digital Rebel has quickly become one of the most popular SLRs out there, but they've introduced so many different models now, it's hard to sort through what is what.

Could someone describe the difference between the XS, XSi, T1i, and the ###D (like 300D, 400D, 450D, etc)?

Also, are all Digital Rebels part of the EOS line?

Last, are the lenses interchangeable, or are the different bodies threaded to fit different lenses?

Thanks!