Yahoo Music Jukebox
It has all the bells and whistles you'd expect of a jukebox, including excellent ripping features, the ability to burn to DCs, and to transfer music to portable devices. You can also buy music from a variety of music labels. There's also integration with Yahoo Messenger, so that you can share music with other users of Yahoo Messenger.
Not everyone has been pleased with the change from Musicmatch Jukebox to Yahoo! Jukebox; some have complained that it's become big and cluttered. And be careful, when installing that you don't install any Yahoo extras you don't want, such as the Yahoo Toolbar, or Yahoo Instant Messenger, and that you uncheck the boxes if you don't want Yahoo to be your default search engine or homepage.