Here’s a software you’d need to clear the unwanted files hiding around your Ubuntu Installation. BleachBit clears up files from your trash, tmp folders, application specific temporary files from Firefox, Java, Open Office  and more. When I ran this on the system the first time, Bleachbit ended up clearing around  188MB of space, pretty good.

This application’s UI is simplistic, allowing you to preview the files which are going to be deleted before actually deleting them. One crib I have is inability to  select individual files to delete or not to delete. You can only remove an application from the delete option.

Download the current version of  BleachBit for your Ubuntu Version and double-click on the downloaded deb file to install. If you want the command line instructions, here they are for Ubuntu 8.10 (intrepid ibex):

wget http://downloads.sourceforge.net/bleachbit/bleachbit_0.3.0-1_all_ubuntu810.deb
sudo dpkg -i bleachbit_0.3.0-1_all_ubuntu810.deb

Once you install it, you can access BleachBit from the Applications>Accessories menu.

Link: BleachBit Project page