The florida weave method. I learned about this from a friend and although I was hesitant at first, when I saw that Johnny's Selected Seeds uses this method to grow rows and rows of tomatoes, I was sold.
The basic principle of the florida weave method is to place tall stakes every couple of tomato plants, then tie twine to one of the end stakes and weave it in and out of each tomato plant. When you get to the stake at the other end, wrap the twine around it, then weave it in and out of the opposite side of the tomato plants. When you're done, every tomato plant should have twine on both sides of it, pulling it tight and straight. Then, every 10 days or so, add another level of twine. Before you know it, you'll have a wall of tomatoes, easy to harvest fruit from.
Because I have limited space in my vegetable garden, I planted 6 tomatoes on an 8 foot row. Tomatoes really need more like 3 feet of space each, but if I keep them tightly supported and properly pruned, they should still produce plenty in 18 inches.
You can use plain tall wood stakes or metal t-posts for the florida weave method. I decided to use the t-posts because they're very sturdy and they'll last forever. Plus, they have a built in hook every 8-10 inches which helps keep the twine secure. Each t-post cost around $5.00 at the local hardware store. I used plain twine that I can toss right into the compost when the garden is finished.
What is your favorite way to support tomatoes?