Slimp3. One of our favorite recent toys has been the Slimp3. It's a very simple device – about the size of a rolled up magazine, with ports for power, Ethernet, and amplifier. It's job is to take mp3 files streamed from a server and play them through the amplifier.
The nice thing about it is that it means you can put all your music on a single server (in my case the Linux box in my basement) and then just use a slimpy to play the music wherever you want it. I have one in the living room and one in the office. You control the slimpy with either a remote control or a web page. You can easily choose playlists, folders of music or whatever. The files are streamed by an open source perl server that runs on the server.
I've gone ultra-automated. Every night a ruby script runs on the server and generates themed random playlists. That way I can have two hour of baroque music followed by an hour of blues without having to make any decisions about what to listen to.
It's certainly made using mp3s a pleasure at home, and now the CDs are relegated to boxes in the basement. [Martin Fowler's Bliki]