Talk about opposites attracting. Deep discount online broker ShareBuilder has rolled out a credit card that -- get this -- puts money into your brokerage account every time you spend.

Getting in on the affinity card business, the company that is known for affordable investing (no account minimums, no inactivity fees, dollar-based investing) partnered with First USA to create a new kind of credit card. Instead of giving you more cash to blow, cardholders earn 1% rebates that are deposited directly into their ShareBuilder brokerage account for automatic reinvestment on a monthly basis.

Now, this is not an excuse to go on a shopping spree just because you think it'll be balanced out by a bigger brokerage account. Do the math -- a 1% reward gets you a whopping $40 towards your future when you buy that $4,000 plasma TV. Still, it's a pretty Foolish twist on rewards credit cards. Cardholders can earn a maximum of 60,000 points per year ($600), and any unredeemed ShareBuilder Points expire after 24 months. And remember, as with most rewards cards, you don't earn points on convenience checks, balance transfers, cash advances, or fees.

We have our own Motley Fool Visa card that gives you the choice of rewards, too, including cash back, airline miles, or points for stuff you might want. But we say, bring on the competition! It makes us -- and lenders -- better.

So if you're a solid card-carrying citizen, shop around for rewards that you can use. After all, shouldn't you get something back for all that time spent finding a parking place at the local mall?