Depends on my mood. I always bring my iPod on hikes and backpacking trips. Most of the time I don't listen to it while hiking, but once in a while I'm in the mood for music and will put in the earbuds.
In camp I usually have music on. I have speakers that fit in the palm of my hand that sound fairly decent.
When I wake up in the morning I always put classical music on. Mozart, Ives, Bach, etc. really make for a great background in the early morning forest.
At night in front of the campfire it's usually mellow rock. Neil Young, Damien Rice, Celtic music, reggae, Nick Drake, Belle & Sebastian, Bon Iver, Leonard Cohen, The XX, Fleet Foxes, etc.
The few times I'm listening to music on the trail I usually put the iPod on shuffle and
shuffle can bring me anything from the Sex Pistols and Beastie Boys to Kate Bush and Miles Davis. With 13,000 plus songs and counting nearly anything can pop up. Ramones, Pearl Jam, Arcade Fire, The Decemberists, Wilco, Johnny Cash, Bowie, Beck, Public Enemy, Kanye, LCD Soundsysem, and hundreds of other artists.