Why not Olympus?
I'm seeing plenty of suggestions, but not one for an Oly DSLR. The E-3 may be a little advanced, but there are several other models to chose from and they all take Zuiko DIGITAL lenses. Sure the sensors are 4/3rds, but with digital lenses, you can cut the weight way down and still get some excellent shots. I would look into an E-520 or an E-620. You can buy an E-620 kit for $649.00. That's a 12.3 MP DSLR with image stabilization built into the camera so no matter what lens you use, it's covered (Oly designed the IS and has been using it for quite a while whereas others are just now catching on to it) and a Zuiko 14-42mm lens. You can get some very expensive lenses that will fit perfectly on this body, but you will be up into the thousands and it all depends on what you're looking to do with it...where your passion lies.