Case-Mate let us know about their latest release dubbed the Case-Mate I.D. The case has a built in card holder which can hold up to 2 credit or ID cards. It also supposedly protects the magnetic strip on your credit card. It only adds 2.5mm of thickness to the phone while protecting it from dings and scrapes.
The Case-Mate ID is selling on their website for $29.99 for the BlackBerry Curve 8300, 8520, 8900, the BlackBerry Tour 9630, and the BlackBerry Storm2 9550. The 9550 and 8900 models are not available just yet but will be coming very soon.
Find them at the links below: