app to map drive?

I need an app that can show me what folders (and possibly files) on my harddrive are taking up the most space, or something to that effect. I only have 30 gb left on my powerbook's disk, so I want to do some spring cleaning and reclaim some space, but I'm too busy to go through every folder and see whats taking up the most space.

Any suggestions?

bump... I really need an app to do this, doesn't anybody know of something?

I do not, but you can use a program called delocalizer, you can look for it on version tracker, and that will erase all the languages in the os that you will not use.. you can choose which ones go and which ones stay. (if you delete all but english it clears up 6.0gb)

This program is useful (I downloaded it and am removing all other languages as I type). But I still need something else.