I find guided meditation quite helpful. I struggle with 'proper' meditation, as my mind wanders too much, and I get irritated, so the guided meditations work well for me. Guidedmind.com has a wide variety of different ones, including one on sleep. Reading for about 20-30 minutes before I go sleep also helps calm my mind... As long as it's something that doesn't require concentration like a Science book. :P
When I find myself getting frustrated because I'm unable to fall asleep, I just tell myself "I'll eventually fall asleep, my body will get the rest it needs", and that has actually also helped, strangely enough. It's as if I've gotten rid of the pressure to sleep and my brain relaxes a little.