If you're anywhere close to the music nerd I am, you know how inspiring a song can be, so why not use that during NaNoWriMo?

Picking the music you listen to while writing is important; it can keep you relaxed, inspire you, and help set the scene.  Are you writing a frenzied ride on horseback?  Maybe a lively Celtic tune would help evoke the scene for you.  A big, sweeping instrumental score can help you write an epic fantasy.  Something dark could be used for mystery inspiration, and something light and fluffy would be perfect for writing a romance.  Maybe hard beats help drive you to finish (it's often that way for me...I listened to a lot of Fall Out Boy last week), or maybe you need something smooth and lilting to keep you from having a panic attack.  Listen to yourself, and listen to your story; you'll be able to tell what you should be listening to.

As a side note, movie scores can be great for writing music.  Several are purely instrumental (less distraction), and they were made with specific moments in mind.  Pick a feeling, pick a song.  It's practically fool-proof!