I've been a member of ebates since 2004. Unfortunately, I didn't realize that I was until Nicole wrote about it on her blog. I think about how many online purchases I've made in the last 6 1/2 years and it kills me that I didn't use ebates sooner.
It's so easy to be a part of . . . you sign up, and then when you want to shop online, search for the retailer on ebates and use their link to take you to the retailer's site. Nothing more to do. Your rebate is deposited into your ebates account. I have $80 in my account from purchases I would have made anyway. I think you get $5 just for joining . . . though I'm not 100% sure on that since I joined almost seven years ago!
Anyway, happy online Christmas shopping.