Sys Admins, Hard Drive Space Running Low?

I'm sure a million people have posted solutions to finding and clearing out unneeded files for those with limited and/or low disk space. When space is running low on your server it's full on panic mode to clean up so that your server doesn't go down. I've had it happen to me many time and only in the past year or so did I find my solution. WinDirStat is a must for any sys admin. It index files on your drive and displays a treemap that allows you to find the big space users and drill into direcotries where you can make the decisions for what you need and don't need.