What a popular thread. I always listen to music when I study and it is always progressive house music. There are no lyrics to distract me and the mixes are usually about 1 hour 10 minutes long so there are no interruptions. Plus it worth it to buy some Shure earbuds. The cheapest ones are like $100 but it's totally worth it.
My iPod is filled with mixes by:
James Zabiela, Nick Warren, James Holden, Way Out West, DJ Icey, Sasha, John Digweed, Danny Howells, James Lavelle, DJ Z-Trip, Joey Mazzola, Mars &; Mystre, BT, Christopher Lawrence, Dave Seaman, Deep Dish, DJ Dan, Ferry Corsten, Lee Burridge, Mark Farina, Paul Oakenfold, Paul Van Dyk, Unkle, Hybrid
Try it. The new John Digweed album Transitions 2 is perfect for studying.