Apple sells a product called the "Airport Express". It is a wireless networking node. You can plug your computer into it to join the network OR you can plug in a pair of speakers - this is called "Air tunes". iTunes allows you to stream music to multiple Airport Express nodes.
My idea is to create a boom-box that has an Airport Express built into it.
Right now you have to take your speakers or boom-box and your Airport Express to your listening spot. You plug the Airport Express into a wall outlet, then plug your Airport Express into your boom-box. If your boom-box needs to use A/C power, you have to plug that into the wall, too.
By merging these two pieces of equipment, you have a single box that can go anywhere in your house and you just plug it in. iTunes will find it and send music to it.
If you have an iPod Touch or iPhone with the Remote application you can control iTunes remotely as well.
There are a number of devices you can plunk an iPod into and have speakers. This is different and, I think, pretty simple to build for someone familiar with electronics. I don't think you'd even need to disassemble the Airport Express.