Choco Moco's SweetFM is a free, open source music application that turns Last.fm into a desktop application.
If you're not familiar with Last.fm, it's a Web-based Internet radio service and social networking site that lets you listen to custom streams of music. The site uses your feedback on the tracks you listen to to "tune" what it plays to your tastes.
SweetFM takes Last.fm out of your Web browser and puts it into a small, dedicated Internet radio app.
SweetFM switches seamlessly between Last.fm and iTunes. Tune to any station and you can control Last.fm with SweetFM's interface; stop the stream and you can use it as an iTunes controller.
Apple Remote support - No need to get up from the couch to skip a track or change the volume.
Endless playlists & preview - SweetFM keeps your playlist filled, and if you want to see what's next on your playlist you can do that in the dock or statusbar menu.
Export directly to iTunes - Move your favorite songs with one click to your iTunes library or let SweetFM handle it for you. SweetFM can automatically export your loved, playlist or all tracks. The track will be tagged with the current title, album, artist and cover.
Buy Albums - The iTunes music store is just one click away if you want to buy the whole album.
Skinnable - If you're familiar with HTML and CSS, you can create your own skins for the player.
Skype Mood - SweetFM talks to Skype and can automatically set your mood to the current song title.
Unfortunately for PC users, there's no word on a Windows version of the app at this time.