Tippr. In fact even if you have this is a good opportunity. Through the end of the day tomorrow you can get a $5 credit to use on the Tippr website if you make a donation of $5 through them. Click here to make your donation. There is a limit of 5 donations and credits per person so you can donate as much as $25 and receive credits for as much as $25! Also if you are an existing Tippr customer and have a credit on your account I think you can use that to make a donation and receive a new $5 credit!
Tippr is a daily deals site much like Groupon. Recent deals include a $100 Travelocity credit for just $50 and a $60 Vistaprint credit for just $60.