The PlayStation Mobile (or PlayStation Suite) SDK has been in open beta for a few months now, and the first apps are beginning to appear. The first is a calculator app for the PS Vita (download link below) and the second is a Tic-Tac-Toe game (no download link available).
The SDK is free to download so you can expect more games and apps to surface. Check out the photo of the calculator app, and video of the tic-tac-toe game below.
[Source: MyPSVita]