I have never read anywhere about feeding ham to a hamster.I have however thru my research read where fish or chicken(boiled or baked) are okay in moderation.
One thing to remember is giving too many treats are not good for your hamsters as with any pet.A few other treats I have found while searching the net include these
Bread (fresh or stale)
Cake - but not chocolate cake
Egg (scrambled or boiled)
Peanuts (shelled or unshelled)