Finding large space hogging files in a complex file system like that on your Mac can be difficult. GrandPerspective, a small open source program, aims to help you find and remove space wasters quickly and easily.
GrandPerspective first scans a target folder, be it your entire disk or just your iTunes folder for instance. It can then build a treemap based on the file size and type, color coding the files in a user configurable mapping scheme, showing you your file system visually. From there you can identify those files and folders that are taking up the most space.
Once you've found an unusually large file you can find out what it is by hovering over it or clicking it, with file information such as name, size and file type displayed in the right hand draw. You can then either delete that file directly from GrandPerspective (if enabled in the application preferences), or reveal that file or folder in Finder.
You can also zoom the treemap in or out to get more detail, as well as re-scan at any time, either just the folder selected or the whole drive to update for any changes you've made. The color mapping can be changed to color like file types, extensions, names, levels or folders, which makes grouping similar files easy. Filters can also be used to scan your files for all sorts of things like file type, size, name -- you name it, there's a filter available.
If you're looking to free up disk space on your drive, GrandPerspective makes it easier to find unwanted space hogs and is certainly worth the free download.
Thanks to aliasnexus0 for the suggestion.