When I've had an upset stomach after eating, it's usually been because I ate something really fatty or greasy. If that happens, I drink something clear and carbonated or something like Gatorade G2 and I *don't* eat anything for several hours to give my system time to recover. When I do eat again, I stick with something light.
If I'm nauseated enough to throw up, I try to eat very, very lightly for at least the next 24 hours, just to give my body a rest. This is assuming something just disagreed with me, and not that I'm sick because of a virus or food poisoning. In that case, it's clear liquids or ice chips.