Ginger worked wonders for me.
Celestial Seasoning makes a wonderful tea which has ginger and peppermint, both a great for nausea. It is part of their Wellness line. It doesn't actually contain tea, so there is no caffiene. (Not decaffinated, just no caffiene to begin with.) I was able to find it at a store that carries vitamins, health foods, and organic foods. I never found it in a grocery store. It worked really really really well.
Click!
You can also get "real" ginger ale at health food stores. It is not the same as Canada Dry or the other grocery-store brands - there is more ginger.
Another thing that worked really well for me was to cut my prenatal vitamin into 4ths. (I still took them all at once.) I think that having them cut into smaller pieces made it easier for my body to digest. I always got nauseous from things that were difficult to digest - pasta, heavy foods, fatty foods, etc.