Makinon lens / Canon Rebel XT?

Your Canon XT only accepts EF and EF-S lenses. Whether it is from a 35mm camera or another Canon DSLR, as long as it is EF or EF-S then it will fit. Canon FD lenses will not fit on a Canon DSLR without the use of an adapter, which isn't something that we should rejoice about unless you already have a number of FD lenses then it would make sense to not put it to waste. Other than that, I think your best bet is to find a lens that has the EF/EF-S mount. The EF lenses from a 35mm will fit a Canon DSLR, but a EF-S from a DSLR will not fit on a 35mm. So, if you want to be safe about it, just look for one that is EF.