Check out this page from the ASPCA Poison Control site on things to avoid giving your dog.
Here's a brief listing of things NOT to feed your dog:
- Chocolate, Coffee, and Caffeine
- Onion, Garlic, and Chives
- Avocado (who knew??!!)
- Grapes and Raisins
- Macadamia Nuts
- Yeast Dough