GWhere allows you to manage a catalog of your CDs and any other removable media (such as hard disks, floppy disks, Zip disks, CD-ROMs, etc...) indexed in a database. With GWhere it is easy to browse your CDs or to make a quick search without needing to insert each CD one after another.
It is open-source, licensed under the GPL andd really tiny. May be useful for one having many discs and a pendrive.