I recently got a Roku Soundbridge. This is a wireless MP3 player with a large, easy to read text display that plugs into your audio/home theater system. It is a very well executed gadget, worked right right out of the box. It is one of the best gadgets I have ever owned, and has nicely replaced my CD changer.
The way the system works is that you run a streaming server on your Windows, MacOS, or Linux PC which indexes your MP3 collection and streams it on demand to the SoundBridge. iTunes and Windows Media Player already have the capability, or you can install a third party free server. The Soundbridge has a simple remote and an easy to navigate menu system, which you use to browse or search for music. It has a built in display, so you don't have to use your TV to see what you are doing, unlike some competor products. It talks wi-fi, so you don't have to run an ethernet cable to it.
The other really cool thing about the SoundBridge is that it can receive internet radio stations, without going through your computer. I use it to lisen to my local AM radio stations in static free digital glory.
I'm not shilling for Roku, just a satisfied customer.