For anyone traveling outside the US you might be in for a rude awakening.
Pandora doesn't work outside the US.
Never fear! The internet will save you! (As usual).
Introducing (something many of you probably already know about...)...8tracks!!!
You can make mixes (haven't done that yet so I don't know how difficult/easy that is), listen to mixes (search by artist, mixer, tags, descriptions), and just generally enjoy music!
It's great. And for added enjoyment, go to rainymood.com and have it on in the background, especially if you're stuck inside all day studying or such.