I also find game soundtracks to be good mind numbing study music. They're usually composed in such a way to enhance emotions in the game but not overpower the player during gameplay.
http://www.youtube.com/watch?v=DvRRwGgNC9s
http://www.youtube.com/watch?v=TMmH6pct_wM
http://www.youtube.com/watch?v=VZxK58tPU4I
http://www.youtube.com/watch?v=V7HZJmPS4U4
http://www.youtube.com/watch?v=LInzl566l7A
There's also a youtube channel called sheepy mixes which makes some amazing chillout mixes.
http://www.youtube.com/watch?v=f9qavey27Kc
http://www.youtube.com/watch?v=F1m_4RsJ76k
http://www.youtube.com/watch?v=DvRRwGgNC9s
http://www.youtube.com/watch?v=TMmH6pct_wM
http://www.youtube.com/watch?v=VZxK58tPU4I
http://www.youtube.com/watch?v=V7HZJmPS4U4
http://www.youtube.com/watch?v=LInzl566l7A
There's also a youtube channel called sheepy mixes which makes some amazing chillout mixes.
http://www.youtube.com/watch?v=f9qavey27Kc
http://www.youtube.com/watch?v=F1m_4RsJ76k