According to this comparison page, the Rebel XT has more resolution than the D50. There are links to other discussions comparing the two cameras.
http://www.vsxl.com/cameras/Canon_EO...Nikon_D50.html

I have no doubts about the quality of the Canon or Nikon, but being on a tight budget, I think the Pentax does offer good value for money wise. MY gf and I both purchased K100Ds for $650USD as a kit.

The beauty of the Pentax (again cost effective wise), is the backwards support for manual lenses which are cheap (I bought a 35mm Takumar in great cond. for $15USD - but thats another story with screwmounts). Not only is the K mount backwards compatible to 1975, you get three major features when shooting with old, vintage manual lenses with the Pentax:

- electronic focus confirmation
- shake reduction
- auto metering

Now I'm a big fan of Takumars, Russians and other vintage prime optics =)