SizeFinder

SizeFinder's main purpose is to show folder sizes in a Finder-like interface. It calculates the size of a folder (own size), and the size of a folder including all of its subfolders (total size).Additionally, you can use wildcards to include / exclude files.

For instance, search for all of your *.mp3 files, or show the size of everything except *.zip.
You can choose to consider the exact file size or the place on disk it uses.