Search window and Dock menu:

Index and search ID3 tags of MP3s on removable media:
(This is a CD a friend of mine made using Windows. Look at the MS-DOS-like filenames that would not allow a search for an artist and the indexed ID3-tags for which you can search.)

Browse offline volumes:

Edit categories for removable media:

New in version 0.7.2: Index and search archives on removable media.
This zip archive is on a CD not mounted. You can also directly search archive contents; how often do you know the name of a file in an archive but forgot the name of the archive... well, that time's over.

Also new in version 0.7.2:
A grep like functionality that lets you search for contents of files. The four buttons below the text view can be used to navigate through the matches.