iTunesFS is a MacFUSE filesystem, written by Marcus Müller, that lets you browse your iTunes music library and playlists from the finder. It's a great example of MacFUSE being put to use, and the source code is available (via Subversion) for others to learn from.
iTunesFS allows you to manage the songs in your library directly. "But I can drag and drop files right from iTunes," you say. Not from your iPod(s), you can't. iTunesFS detects iPods, and allows for direct control over the music contents. It also offers a view of your playlists with sequentially numbered filenames to preserve playlist order. If you're handy with Terminal, it's a simple task to customize the formatting of the naming scheme as well.
iTunesFS requires MacFUSE, available at Google Code.