I wrote this script a while back to get a snapshot of my disk usage. Since I'm using a powerbook and hard drive space is limited, I thought it wise to make sure I didn't have too much garbage lying around my drive.
To use this script, simply download the disk_usage.pl file and place in a good location on your hard drive. Once you have downloaded the file, open up the Terminal application. Run the command:
chmod 755 /path/to/file/disk_usage.pl
Once you have set the execute permission, you can now run it.
perl /path/to/file/disk_usage.pl /your/dir/here/