One more method for trellising tomatoes.Last summer I took a series of classes from these folks, who are a great resource if you're in the Madison area. For the tomato class, they had no less than four or five methods for trellising tomato vines. Any or all of them work great, it's just a matter of what works for your space and budget.
For years I used oversized tomato cages which I got a bunch from a garage sale. Of course they aren't enough support for big healthy indeterminate plants, so we always staked them with whatever we had around--t-posts, wooden stakes, etc. But as the garden grew the number of plants did as well, and we're now hovering at about 15 tomatoes a year: not enough cages. And then last summer's brand new garden beds (fresh soil!) grew gargantuan tomatoes, so new measures were required. We pulled some conduit pipe out of the garage rafters and made eight-foot stakes. This, and a modified method from class did the trick.
This type of trellising does require pruning, I don't think it could support a fully wild plant. Our class taught to prune to two main stems, and I'm fairly religious about this early on (once they are setting fruit well I mostly let them run free).
So far I'm pleased. One thing I like is not having to rein in a rogue branch, I can just catch it up in the support the next week if one escapes. This is a fairly intensive planting--I have seven vines in a 4 x 8 bed--and most years it turns into a jungle. This year I'm keeping them mostly in line, or at least they are not strangling each other! With diligent pruning this density of planting is just fine, especially on a very dry year like this, where disease is pretty much a non-issue. Your mileage/climate may vary.