Ebates is a cool service. Basically, you start your online shopping from their site, and then you get a cut of that merchant's referral bonus. Simple as that. I actually get checks from them, and I haven't gotten a single spam mail yet in a year, which I know for sure because I gave them a uniquely identifying email address like I do for every site. That way, if someone does spam me, I'll know who it was. So far, the only site to have ever sold my email address was Uproar.com.
Email me if you want $5 free and I'll refer you. :)