Linux/Windows: While Windows already has the immensely popular CCleaner, Linux users lack a good program to clean up their drive. Enter Bleachbit, which frees disk space, shreds files and overwrites free disk space with a simple checkbox-based interface.
Bleachbit has a very simple, two-pane interface: one with a list of installed apps and cleanable areas (like caches and temporary files), and one pane to tell you what types of files each option deletes. Just scroll down the list, check which boxes you'd like BleachBit to clean, and hit the Delete button. You can even tell it to overwrite the files to hide what was originally there, if you're particularly privacy-conscious.
Apart from cleaning a long list of popular apps, it can perform some more advanced tasks too, like clearing the memory and swap partition, delete broken shortcuts, delete languages you don't use and some other application-specific functions. Windows users may be underwhelmed, but Linux users will find this a welcome tool for freeing up a bit of space.
BleachBit is a free download for Linux and Windows.