iPad Sleep Timer

I use Dozzzer for music, the cool thing about it is that it'll fade the sound for you so that when it turns off, it won't wake you up.

http://itunes.apple.com/us/app/dozzzer-music-to-drift-off/id429674741?mt=8

Oh, and there's a trick to listening to videos with the screen off if you'd like to try.

Open the video, lock the screen (video should stop playing) and then press the home button two times (quickly), and then you should see the iPod controls pop up, and then you just hit Play and the video will play and you can turn the screen off.