I have a Nikon D70, have owned it since it first came out, a superb camera let down by the fact there is no provision for a cable release, annoying but I can get around it and have many a time, grrrr, stupid transmitter.
But if you want to go for a system, then either Canon or Nikon, they are just about as good as each other. I only got Nikon because the then Digital rebel did not feel so good in my hands. But I also run a Canon S70 as a back up to my Nikon so brand wise, I am not loyal and will not push either over the other, as it is all down to how what you choose feels comfortable in your hands. Swings and roundabouts as they say.
But there are other makes that are worthy of attention, as mentioned, Pentax, Olympus and Fuji are worth looking at, but again it is all down to what you need and how far you envisage going with the DSLR route.
Yeah, and don't be conned by the megapixel race, as megapixels are really just salesman talk. Think how big you are likely to print a picture and how big that picture is you have to step back further to take it all in thus rendering a myriad of megapixels , really a waste of time.
My D70 runs 6 megapixels and the S70 7 megapixels, I can't see the difference and what I have has served me so well so far, why jump into the megapixel race.
But a website worth a look, Ken Rockwell knows his stuff ;
http://www.kenrockwell.com/tech/recommended-cameras.htm