Locked in the App Store

Oh god, I can't seem to find my way out of the App Store. Ever since I got my mits on the lovely iPad, I seem to be stumbling over app after app that I just have to try. Plus with an iTunes account, it doesn't seem to hurt so much....well, not until you add up all the receipts that come through. And since when have I had an interest in historical maps? Or the Periodic Table for that matter?