I am in the market for an entry level DSLR. One model that interests me is the Canon Rebel XS. I also found a rebate of $50 for it. To qualify for the rebate, you need to have a previously registered Canon camera and you also need to purchase your new camera through authorized Canon dealers.
If you go online and search information about authorized Canon dealers, you can find some lists from some online communities. Those lists are dated. Some companies are even out of business already.
Finally, I found an official list from Canon USA. Here is the direct link to the file.