Make:

Make subscriber Nic used Arduino plus Parallax RFID reader/tags to make his Squeezebox network music player a bit more physically intuitive/interactive.

I'm not the first to think of controlling music with RFID, somebody made a pretty neat player called PlayStand way back in 2002. But its RFID reader was plugged directly into the PC. I didn't want a PC in my living room, I wanted the player to be totally self contained, which seemed possible since the Squeezebox was already responsible for playing the MP3s. All I needed to do was trigger a song to start playing once it saw the tag. Problem was that my server is in another room and I don't have an ethernet drop in my living room. There are ways of making Arduinos work with Wifi, but they are all really expensive, so after a bit of looking around I remembered that the Squeezebox itself could act as a bridge. So the arduino actually connects via ethernet to the Squeezebox, sending commands to a little PHP script I have running on the same server as the SqueezeCenter. That script provides a management interface to map RFID tags to particular URLs, so after configuring it, when it gets a message that new RFID is in place it triggers a playlist to start. You could use this same system to perform other actions that can be performed via a script, such as having a coaster both stop the music and post a tweet that you are off to work or somesuch. But I'm just using it for music.