BleachBit: keep your system tidy and clean

An extremely easy to use application, BleachBit will scan your Linux system for thumbs.db files, system and various application cache directories, old log files and will also wipe empty space if you so choose to ensure privacy. It is aware of many applications and knows exactly where their cache files are located. I found it not only reclaimed a good chunk of disk space from hundreds of .DS_Store files, and Thumbs.db files, but many cache files from programs I had since removed many months ago. (It also runs on Windows).

From their home page:

BleachBit quickly frees disk space, removes hidden junk, and easily guards your privacy. Erase cache, delete cookies, clear Internet history, remove unused localizations, shred logs, and delete temporary files. Designed for Linux and Windows systems, it wipes clean 70 applications including Firefox, Internet Explorer, Flash, Google Chrome, Opera, Safari, Adobe Reader, APT, and more.

It is available for most Linux distributions. Here is a great write-up on it from Linux Magazine.