The Squeezebox is a very popular product these days. There are a number of other products around that are similar (Roku Labs Soundbridge, PRISMIQ MediaPlayer, Apple's Airport Express, and a bunch of devices from folks like Linksys and D-Link), but Slim Devices seems to be the dominant player. I think that PRISMIQ is actually discontinuing their MediaPlayer. I've considered picking up a Soundbridge since it's a bit less expensive than the Squeezebox (the M500 is available for $150 and the M1000 for $200, both with support for wired and wireless), but I haven't decided yet. Slim Devices definitely seems to be the most on the ball about providing good software support (I'm not a huge fan of SlimServer's interface, but it's effective and they've been good about improving it steadily) and they've done some good things with the hardware (adding good quality DAC's to the Squeezebox 2 and moving to a fancier shell with the Squeezebox 3).

I'm not sure that you can get access to a remote music library unless you have VPN access to the remote site or you have the remote site providing a streaming Internet channel that the Squeezebox can tune into, but the forum that mzpro5 mentioned could give a more definitive answer.