If you use background music only for noise cancellation (crying babies, reconstruction works etc.), I recommend http://www.simplynoise.com/. It's not as distracting as even the most minimalistic trance.
Ah nice. Definitely bookmarking this. Also related, I started using rainymood, fireplace and jazz loops found on a reddit thread from a while back [1]. After using different combinations of the 3, I've found that sometimes music doesn't cut it, and a simple fireplace/rain loop helps me work better.
[1] http://www.reddit.com/r/reddit.com/comments/ca4bl/time_to_ge...)