If you're a DJ or music aficionado with a large collection of CDs and/or LPs, you know that keeping track of them can be a chore. VisiTrax Lite is a free librarian that helps you catalogue your tunes (automatically for CDs by looking them up in an online database).
Then VisiTrax Lite can easily find them using a number of criteria, including the usual artist and song name - but also extending to media format, era, BPM (beats per minute), and even how long the song lasts.
VisiTrax Lite's interface is no-nonsense and easy to use. It's not as pretty as say iTunes, but it'll get the job done quicker.
VisiTrax Lite also has some nice I/O options including CSV export to spreadsheets as well as uploading to the http://www.djintelligence.com/ and http://www.wedj.com/ DJ booking sites. Note that VisiTrak is not a player, though. It only catalogues and is therefore of limited use for MP3 collections.