I've been a long-time fan of Slim Devices' MP3 hardware, the SqueezeBox. $300 for a little box with network in, audio out. I've used one for years to play my MP3 collection on my kitchen stereo.
I recently updated everything and learned that Slim Devices has greatly expanded their network capability. The player has morphed from something that just plays your MP3s to something that streams audio off the Internet. I'm now able to easily listen to Live365 radio (hello, SomaFM!), Shoutcast stations, my Sirius radio subscription. With the new SqueezeNetwork setup you don't even need to run a server in your house; your player can connect directly over the Internet to public streams. There's some sort of iTunes integration, too.
The coolest thing I've found so far is the Public Radio Fan Browser, a user supplied addon that uses the program listings at PublicRadioFan.com to find me an audio stream playing a public radio program I want to listen to, right now. Terry Gross, any time of day! Hey, Ira Glass, entertain me while I'm mixing cocktails! Or is it bedtime and you can't go to sleep? Just tune in Prairie Home Companion! All so easy.
And just to go full circle, there's even a Java app that emulates the hardware on your desktop PC. Seems odd, but it means Ken and I can listen to my music the same way on my home stereo or my PC. It's great.