If you are looking for the best affordable DSLR on the market, no need for further research, Canon Rebel XS 10.1MP Digital SLR Camera with EF-S 18-55mm f/3.5-5.6 IS Lens is absolutely better than Olympus E-510 or Nikon D40/60.
The next question is, where can you get the best Canon DSLR deal?
Based on leaked Black Friday deal info, Walmart and Sears both have it for $479, but after adding tax to it, your total take home price will be $500+, plus you have to compete with those early birds (3am? 2am? or even earlier?) to be the first group getting into the crowded Walmart or Sears retail stores.
Amazon's regular price was $650 which was not attractive at all. However, now it's only $499, making it instantly the best DSLR deal for this Black Friday. I have grabed one today, do you still need more research? Read Amazon's product reviews will help you make up your mind.