Possibly any of you who are interested are already signed up for this, but in case you're not: Ebates is a website that gives you back a percentage of your purchase price when you shop through them.
You have to sign up and log in, then follow the link to the appropriate online store from their site, to get the rebates. They mail out the checks every three months, and you have to have at least $5.01 in spending rebates to get the check.
They also have referral bonuses, and they're currently doing a promotion on those. Referral bonuses don't count toward the $5.01, so this only does you any good if you use the shopping feature, but they do count as money, so. ;) At the moment, the bonus for referring a friend who makes a purchase, or for being referred, is $10 rather than the usual $5.
My referral link, should you choose to use it. ;)