I love heavy metal to study to. Some surgeons I worked with would put a website called "Pandora" - www.pandora.com - during their cases. You can put in genre or artist and it will play similar music.
The Beatles, The Doors, Pink Floyd, The Stones, Queen, Zep, Ramones, Sex Pistols, ACDC, Iggy Pop, Lou Reed, Sublime, Bob Dylan, Johnny Cash, Grateful Dead...that's the REAL DEAL.
well, i personally listen to mostly R&B when I study, but I do tend to venture out to other genres...
One of my favorite avenues for music (and lots of variety, when I need it) is an online radio site, such as www.vh1.com (which is an excellent online radio, with few commercials) or www.aol.com.
Personally, I like jazz. Makes me feel smart, plus no lyrics to distract the mind. I've found that Miles Davis' "Kind of Blue" album is an ideal soundtrack to basically any of life's activities, especially studying. "Miles Ahead" and "Porgy and Bess" are also good ones.
A great free internet radio station is yahoo's launchcast and the station with some good downtempo stuff is "chillout" the only downside is that there is commerials every few songs.
Another great source of free music esp if you like live stuff is the live shows section at NPR's All songs considered. Some of the best musicians around right now i.e. Arcade Fire, Cat Power, Ray LaMontagne, Ted Leo, Modest Mouse, Ben Gibbard of Death Cab, and my current favorite band...The National.
I just found accuradio.com a few weeks ago and I LOVE it! You can pick a genre and it plays a mix of a bunch of stuff within that genre. It's basically like satellite radio but you don't have to pay for it.
Also another metalhead here. I usually study with a mix of old school thrash (Anthrax, Slayer, pre 1987 Metallica), 70's metal like Black Sabbath and Motorhead, progressive rock (Rush, Dream Theater,NIN, Coheed and Cambria) and more recently weird electronic music like Battles.
Thanks to all for the replies. Something strikes me as interesting, especially with the metalheads (I like metal a bit too, for the record); does anyone else find that listening to "your favorite music" is too distracting? As stereotypical as it sounds, I've taken to new-age, ambient stuff because there's no heavy lifting involved. I know that everyone just got the image of the uber-cerebral, "free-your-mind" med student, very intelligently crouched over his books, approaching intellectual nirvana, and went "PFFFT !" - but if I put on some Metallica, Audioslave (knock them if you will, but nobody can scream quite like Cornell), or BRMC, then I start to put down my books and pick up the air guitar.
free, pretty much every genre out there, not too many commercials, easy to save favorite stations....and easy to change things up if one station isn't doing it for you!