Sounds more like flea beetles. If that's the case, they probably are not a big threat, though they can eat a lot of tiny holes in the leaves (especially yellow or necrotic leaves). I think they are mostly only dangerous to young plants.

However, if there were enough there that they were easy to notice, that might mean they are dense enough to cause trouble.

http://www.extension.umn.edu/distribution/horticulture/M1210.html

If there were "tons" all crowded together, I think they were probably aphids.

Aphids come in many colors, and those which like tomatoes may be green, yellow, pink, or black. Some have wings and some don't (different stages of growth, I think). Pics at the link below.

Spraying them with soapy water is supposed to work. And if you're lucky, predators like ladybugs, lacewings, and praying mantises will find them soon.

Here is a link that might be useful: http://images.google.com/images?gbv=2&hl=en&sa=1&q=aphid+tomato&btnG=Search+Images&aq=f&oq=

If they have clear wings they might be fungus gnats. They are attracted to moist soil. Here's a link with a good picture.

Here is a link that might be useful: Fungus Gnat

With regard to the first reply, flea beetles indeed can be very harmful to tomatoes and eggplants. The very reason infested leaves become necrotic is from the flea beetles sucking the life out of them.