Recover erased files from your microSD card with the Undelete Beta app for Android
It works for pictures, music archives, videos, binaries and so on. Swift operation is ensured by its fast scanning logic, and it also gives you the ability to permanently erase files, i.e. shred them beyond recognition in case inquiring minds might get to your dirty little secrets.
It is still in beta and the developer gives no guarantee it will recover everything on every device, but it's free so we wouldn't expect it to anyway. Undelete Beta has been tested on most high-ends like the Samsung Galaxy S II, HTC Sensation and Asus Eee Pad Transformer, among others.
source: UndeleteBeta (Android Market)