Pentax K100D
The Pentax K100D may be the camera you are looking for if you want to go digital with an entry level SLR and have Pentax KAF2, KAF, and KA mount lenses (K mount lenses work with limited funtionality).
DP Review just published a full review of the K100D and gave it a HIGHLY RECOMMENDED rating, their highest. Image quality is significantly improved over the Pentax *st DS, is better than the Nikon D50 and very close to the Canon Rebel XT (350D). Read the full review for more details.