cleaning out the computer

What are easy ways to clear out the random crap I have in my computer that I don't use anymore so I have more space?
I've done disk cleaner, defragmenter, and uninstalled some crap programs.

Is there a way to look for folders that hold the most space?

This little thing have a builtin virus checker, autodisk repairer, spacesaving hda utilites, absolutely freeware, builtin NEROBURNINGROM-like programs to write cds, openoffice for everyday work, vim/emacs for programming, full collection of development tools just from the box, no ads or additional payments - and its all just in one single click:

http://goodbye-microsoft.com/

<trollface>Not a virus or a keylogger, not a ubuntu!</trollface>