Here is a link to the most useful hard drive space analyzer I have ever come across. While it does make my geek bones tingle, it's not just for computer geeky-types. It's also useful for video editors, graphic designers, and sys-admins. Okay... it is for geek types, but it's so useful I just had to shout it on high from the mountain tops.
What it does is analyze your hard drive and give you a very simple view of your directory structure based on how much data is stored in that director as a percentage of your overall hard drive usage.
The upshot is once you have run it, you can easily tell what files and directories are taking up the most space on your hard drive, and easily drill down to those directories and do some house keeping. It's great for finding out where you can free up some space on your hard drive.
This utility will likely become less and less important as hard drive space increases seem to be out-pacing software space requirements.
Oh, it's also open-source, so you can hack to it your heart's delight and have it do what not with your files. I love it!
The web page for the Util: http://windirstat.info/