1. Tea - There hasn't been much written on dying with herbal tea (or at least as far as I have found.) But there has been some written about dying with black tea. There is a good tutorial on KnitPicks and another one here.
2. Coffee - You can't have tea without coffee, right? Re-Nest lists dyeing as one use for coffee grounds. This blogger dyes with coffee all the time. I also found this tutorial.
3. Beets - I wonder if there's a way to make a dye bath, then eat the beets. There's a tutorial here that talks about using canned beets as a possibility.
4. Turmeric - Turmeric is a spice right? (Can you tell I don't cook?) Anyway, there is a good tutorial on instructables, and the color is gorgeous.
5. Blackberries - Blackberries are too expensive to just use for dye. Maybe I can make some sort of dessert with the leftovers? It's beautiful, though. (Check out this tutorial.)
6. Juice - Grape juice is the one that comes to mind. (It's the one that stains, afterall.) However, I imagine other juices will work as well. (I found a grape juice dyeing tutorial.)
7. Onions - I hate onions. Blech. But onion skins make a pretty yellow. (Lion Brands has a tutorial.)
8. Cabbage - I like the color of purple cabbage. I found this blog entry where they actually ended up with blue, not purple.
9. Food Coloring and Easter Egg Dye - They aren't quite food, but they are edible. Perhaps safer than some of the others, because you don't have to add any unsafe additives. The best tutorial ever on the topic, including microwave instructions, is here.
10. Kool Aid (or a generic equivalent) - I saved the best for last. How can you talk about dyeing with food grade dyes and not mention Kool Aid? In case you haven't heard, Kool Aid dyes yarn very well. (There's a reason why it's so hard to get the stains out.) I dyed the yarn above with Kool Aid and Hawaiian Punch. Knitty has an excellent tutorial, and there's even a color card online.