It really depends. Most often: none at all. At other time, it can range from classical to '80, and from tango nuevo to gothic metal. When I don't want to be destracted too much, I tend to listen to movie sound tracks.
Looks like this thread is live again, hehe.
For me it depends too. Most often is some blues or jazz. For now I'm from time to time listen FolkAlley radio.
I prefer a quiet environment. But sometimes I listen to smooth jazz and slow RnB instrumentals. That way I don't get distracted by the words of an artist.