IndyMom, you can find some really nice things on the internet. Check out Kittybids.com or Ebay. I found keychains and wooden boxes that were engraved with sayings like "Homebirth is where the heart is" with a pretty picture of a baby in hands. You can also do a search for pregnancy products and alot of websites have a selection of gift items (little figurines, knickknacks) that are all birth themed. You can also give them little aromatherapy kits that they can use on themselves or thier clients.
It is not uncommon for women to send the L&D nurses things like gift baskets of food or lotions or things like that. It really did make you feel like you had made a difference and appreciated.