I like classical music as background music... almost like muzak. When I listen to it as background music, I tend to prefer baroque music. But other times I like romantic or even 20th century music, too. FB friend Jason Clemens recently pointed me to the KDFC website, where you can listen to music, and it seems pretty good quality streaming. I'm sure there are many other sites that provide classical music, too, but I thought I'd pass this along especially to my friends who miss what CBC-FM used to be.
Also, if you still like and use CDs or will use Amazon's cloud for music, you might want to consider their classic albums (not just classical music; pointer from Joshua). There are some amazingly low prices there.. . . .