Anything with caffeine - coffee, chocolate, some pops (Colas, Jolt, Mountain Dew). Some teas are caffeinated as well.
In addition to foods, if you're having trouble sleeping you may need to modify your sleep environment.
1, No TVs in the bedroom - train your body that bed is a place to sleep, not watch tv.
2. Complete darkness - so use black-out type material on the windows.
3. Cool temperature.
4. If you have a lot on your mind, write it all down on a piece of paper and tell yourself you'll take care of it in the morning. Otherwise you may end up tossing and turning all night long because of those things on your mind.
I find I naturally get sleepy at a certain time. If I stay awake past that because I'm watching a tv show or reading, I get energized and then it takes longer to fall asleep.