Music To Test By: Portal 2's Free Soundtrack
Attention, test subjects. There is a soundtrack to Portal 2, and it is now available for you to download. It is free (FREE!), and comprises 22 MP3s with a bitrate of 320kbps - which is a number than means it doesn't sound like a man yodelling into a fish tank. Appears to be purely the instrumental soundtrack, not the Coulton or The National songs, but that means it's full of bleepy, technoid wonder. You can get it from here.
This is but Volume 1, which suggests a further volume to come (edit - two more, in fact). If you're the sort of person who likes annoying people on the bus, you can also download snippets of some of the tracks as ringtones for your personal communication device.