Mr. Rebates just added 1% cash back for winning bids on ebay. Yea!
So far, I've been really happy with this company. They offer higher cash back at some of the online stores that I shop at (Buy.com for example) than similar companies. I actually haven't found a store where they aren't competitive with their cash back offer.
They have been pretty good about crediting my account, but in the one case I had to make an inquiry, they responded quickly and credited my account while they investigated.
Their payout is $25 and rebates remain pending for a few months to make sure that you aren't trying to scam them by making returns. However, they have a referral program, and if you shop a lot online like me, the cash back adds up pretty quickly.
They also give you a $2.50 Bonus just for signing up.