Not necessarily a chip music exclusive item. Really, anyone with a pair of speakers and no amplifier to drive them could use this. The design appears in MAKE Magazine issue #23. I've been working off and on on it for the past few months. I made a couple changes over the version presented in the magazine. I replaced the perf board with a printed circuit board I designed myself and had made by BatchPCB. I also did not need the switch for two inputs or the volume control (I'm just going to use the volume control on my computer). Soldered up the board last weekend. Just need to make something nice to store it in.
http://www.youtube.com/watch?v=G_DVLNO-Rxs
You can find out more at my own website, gilberti-industries.com, or at makezine.com/23/chipamp.