Are there any good vitamins or supplements that help with insomnia?

Serotonin foods. Anything which helps regulate sleep may improve the situation (avoid caffeine and more than one drink of alcohol after 3pm, regular sleep, avoid stress or shift work), as well as serotonin foods 30min prior to bedtime (dark chocolate, almonds, glass of milk, banana, dried cherries).
Yes. Melatonin is a naturally occuring brain hormone that cycles daily. Taking a melatonin supplement 1-2 hours before sleep can help regulate your sleep cycle. Warm milk is not a myth; it works. Try camomille tea too. A variety of homeopathic remedies can help, depending on the nature of your insomnia. Above all, practice good sleep hygeine and go easy on the caffeine.