Fire.fm is an add-on for Firefox that embeds an audio player to give you direct access to the library of music available from Last.fm.
As with Last.fm itself, you don't choose the track you want to listen to, but enter an artist name, and it will create a radio station of similar music. As Last.fm users may tell you, this can be a great way to discover new music you might like, and is a good way to take a break from your own library.
The add-on has a 'Visit Last.fm' button, and 'Log in to Last.fm' button so Fire.fm can scrobble what you listen to. Clicking the Last.fm logo will give you options to start a new station, and listen to your previous radio stations. If you have a Last.fm account you can also listen to your top artists stations, friends stations and neighbors stations too.
For users of Last.fm and Firefox, this is a great add-on because once you're signed in you needn't have the web page open, which saves you valuable tab space. The interface is very easy to navigate around, and keeping a list of previously listened-to stations is a really great idea. If you don't have an account with Last.fm, the features are much more limited and feel less personal.
Fire.fm is a nice little addon, and a cool way to listen to music from Firefox.