(MONEY Magazine) – The amount of money spent online increased by about a third in 2003--and more and more websites want to give some of that back. Butterflymall.com has joined Ebates.com, Fatwallet.com and Rebateshare.com to reward you for surfing to their sites en route to retailers. Typically merchants pay portals a fee for sending buyers to their sites; the rebate sites pass part of that fee on to you. The typical rebate: a modest 4% of your purchases. But since you can combine the rebates with any other coupons or discount codes, you can rack up real savings. Most rebate sites won't cut a check until you earn a minimum ($5 to $25), so pick the site that offers the highest rebates at your favorite merchants and stick with it. Butterflymall.com partners with more than 500 retailers, like Gap and Barnes & Noble. Fatwallet.com lets members of PayPal cash out at any amount. Ebates.com, with more than 700 partners, is the easiest to navigate. Rebateshare.com also offers coupons. --M.J.