Well, as I see it, you have four reasonable options:
1) Canon EOS Rebel XT
2) Nikon D50 (while they are still available)
3) Pentax K100D (my choice)
4) Olympus E-500
They each have their strengths & weaknesses.
Canon Strengths: Highest resolution, accurate color, excellent processor, excellent accessory support.
Canon Weaknesses: Tiny body is too small for mens' hands without feeling cramped. Plasticky, cheap-feeling kit lens, no spot metering, no image stabilization, unless you buy the expensive lenses.
Nikon Strengths: Most comfortable body to hold, excellent accessories support, probably the toughest chassis, good color accuracy.
Nikon Weaknesses: No image stabilization
Pentax Strengths: Comfortable body to hold (not quite as comfy as the Nikon), image stabilization built into the body, the best kit lens. (steel lensmount!)
Pentax Weaknesses: Not as many third parties make optics and accessories for Pentax as for Nikon & Canon. However, Pentax lenses are VERY good, and are quite reasonable compared to Nikon & Canon's equivalent equipment.
Olympus Strengths: Lightest body in the class, and the only one in the class with ultrasonic dust removal on the sensor. Excellent Zuiko optics. Very comfortable to hold. Adapter available to fit older, manual focus Zuiko optics, which are among the world's best and very inexpensive on the used market. Great price for a high quality setup, probably the best in this class.
Olympus Weaknesses: 2X multiplication factor due to small sensor means you won't be getting any good deals on wide angle lenses. Smaller sensor is working pretty hard to keep up with the bigger ones on the competition.
Read up on these 4 cameras at dpreview.com and steves-digicams.com. Make some time to drive to a big, well-stocked camera store to check these out. Fill in your location in your profile. There may be someone local to you who would be willing to show you a few things. I know I would if you are in the Chicago area.
I chose the Pentax because of the image stabilization built into the body, (the only one in this class to have it) the excellent quality of the kit lens, accurate color rendition, very low noise, even at high ISO settings, and previous good experience with Pentax durability and optical quality. (K1000)
There are good reasons for each of them, and to be honest, you would probably be happy with any of them. If you were comparing them by looking at prints, they'd have to be VERY big prints for you to tell the difference.