The things I do during play really depends on my mood.
Sometimes I go on my instant messenger and talk past hands with friends during one of my tournaments, and maybe things I should have done. Other times I want to stay concentrated and play in complete silence without any distractions.
For the most part I talk to friends about my game, listen to some alternative music, and if I feel like it, the rap music.
Like someone said earlier I also like to watch comedians, but it is much harder to watch youtube videos while playing, so normally I just listen to them unless they are a visual comedian.
It is important in poker to stay completely focused but when you are sitting at a computer with instant messengers, web browsers, and other things, it is hard to keep that complete focus, but sometimes that helps people.
By the way when I do listen to the rap music, I crank the volume and bass on my computer sound system, my house shakes.