For whatever reason you might find yourself one day missing all your pictures form your digital cameras SD card. No need to be desperate, there is a great piece of open-source software called PhotoRec that can help. Although it sports no GUI it’s not really necessary after all, it’s pretty straightforward.
In Ubuntu 12.04 you can install it via the Software Center choosing the metapackage testdisk. After successful installation PhotoRec can be started in a terminal (Alt-Ctrl-T) by the command
Here choose your device and filesystem you’ll like to recover data from and a destination with sufficient space where to save the recovered data. Recovering a full 8GB SD card took approx. 10h for me, so maybe plan an overnight recovery.