It's freaking me out, but my tastes have totally changed over the years. It used to be The Dead Kennedy's and 70's punk, but lately it's minimalist modern classical, like Robert Rich or David Darling...
Reich is somebody who I've been introduced to in the last couple weeks. I haven't tried him yet, but I find his work absolutely mind blowing...and exhausting to listen to. It's like a really great hike up a mountain, watching the scenery slowly change the entire way, then absolute exhaustion at the end of the climb.
Steve Reich is another Reich worth listening to. My work/concentration playlist has Music for 18 Muscians, Violin Phase, and Octet. All great minimalist pieces that are interesting enough to keep your mind engaged, but not too distracting.