I found a site on the web that listed quite a few items that could be used:
Kava Kava
Chamomile
Passion Flower
California Poppy
Skullcap
Hops
Cowslip
Great Mullon
Bugleweed
Jamaica Dogwood
Mistletoe
Lemon grass
Of course I have no idea what preparations are needed to make some of these ingredients helpful, but research it...you wouldn't want to poison yourself or anything, or use it in an unaffective manner.
You might also consider our big thread on aromatherapy here too, a lot of us have added scents that we found useful to us relaxing or falling asleep.
Yoga, life coaching, therapy, these things also make a big difference as well.
It's pretty obvious there is plenty of information on the web about holistic sleep aids and things to help you relax. But it's going to take some research on your part to find out what you should and should not do. Some active ingredients used in weeds and things are used in modern medicine no doubt, so be careful.