Depends what you are shooting for - if you are shooting for yourself, any camera that is small and takes great pictures would do. If you need some pics for a magazine, then you can start using a more expensive DSL.
I use a Canon 40D alot, but either buying the Canon 7D this weekend, or Canon 60D in two weeks or so. Isaac has a variety of cameras, but I think he also uses the Canon EOS 5D Mark II. However, the lense does matter, depending on what you shoot. Those lenses can cost as much as the camera does sometimes.
Price on these vary greatly - a Caon EOS 5D Mark II can cost about $2,200, while a 7D can cost about $1,600, as a 60D will cost $1,100.