I am old school and have a Canon EOS50E. My next camera will probably be another film jobby off ebay where such pro film gems as the EOS 3 now go for a couple of hundred quid if that.
However for digital I would get a Canon DSLR for the lens availability and the fact that I've already got Canon lenses. Just look at any sporting event - the white lenses are Canon. Nikon are good too and photo forums are full of Canon/Nikon flame wars rather like the Shimano/Campag argybargies that we bicyclists enjoy.
One thing I would check is shutter speed ie any lag between pressing the button and the thing actually responding. It may not be a problem with DSLRs but certainly is on even the better compacts as I found at school Sports Day and stage 1 of 2007 TdF.
An excellent site is http://photo.net/ which has advice, reviews etc