jc36lect3r
Forerunner
No Canon (eos) body have inbuilt motor. Only some Nikon's have it its an old feature of cams.
Hmm. Guess what, I was wrong. Every Canon lens after 1987 has inbuilt focus motors, and will focus with all EOS bodies. Canon switched to the EF mount and cut off support for older mounts in 1987. Nikon kept support for older F mounts and also released bodies without autofocus motors like the D5100. These bodies will not autofocus with old Nikon lenses which do not have in built focus motors, but I don't think you will come across those lenses anyways.
So, this point is moot for new DSLR users. Only seasoned people who might own a lot of old lenses might find D5100 lacking.