For a long time, I've loved listening to violin concertos while studying. It seems to put me in a state in which learning flows much easier. My favorite violinists are Midori and Sarah Chang. My favorite composers are Mozart and Bach.
I recently started playing violin after learning about how famous people of the past such as Einstein and Thomas Jefferson played when stuck on problems. I actually wanted to start learning violin earlier in life, so these stories of how the violin helped other people in the past really motivated me to go ahead and start taking lessons.
The Einstein Factor actually claims that when some people listened to Mozart for a while, their IQ points went up temporarily. Interesting I guess.