Amethyst is a good one from off of the top of my head. Supposedly it can ward off nightmares, relieve insomnia, and brings insomnia. Make sure that you don't get a dyed stone. The selenite that I have been using I have noticed that I was better able to remember my dreams. They have been a little more wackier then usual but thats no biggie. Sodalite and Lapis Luzuli are two other ones that meditation stones but I don't know much about them. Hope this helps a little...
Cheers,
Danielle*****