Succession plantings are the way to go. I learned a neat trick from Joe Lamp'l, the host of Growing a Greener World, where he removes the suckers growing between the main stalk and branches on a tomato plant and instead of throwing them away he uses them for his succession plants. Within a week you'll have a young plant that would have taken weeks to grow from seed. As you can see from this picture, all those little hairs on the stem of the sucker are potential roots, so suckers make a quick and easy way to get a succession crop of tomatoes going. Some people will stick them in water till the roots start growing but you can stick them in dirt and they'll grow as long as you keep the soil moist.
