The bad thing about Big Crumbs is you only get a small percentage of the seller's closing fee, NOT the price of the items. Unless you're buying high priced items it will take forever to make enough on Big Crumbs to be worth the effort.
I use MyPoints.com. you get 2 points for every $1 you spend on ebay (10 points during the holidays) and with all the other ways to get points on there, I get a $10 gift card every month.