I wrote in my "how to grow healthy seedlings" post that you should be careful not to plant under the lights too early. My example was tomatoes. Kimberley from The Life of a Garden and some others have expressed concern now that their early-started tomatoes might get too big and leggy before planting time.
I didn't mean to scare anyone. If your tomato plants do get leggy, don't worry. You can always correct that at planting time by burying more of the stem.After the danger of frost in your area has passed, you should plant too-tall tomatoes very deep in the ground. This encourages adventitious roots to develop along the buried portion of the stem. Its also okay to snap off the lower branches if necessary.
If you can't get a deep enough hole, you can plant the tomato sideways in a trench and carefully bend it upright so the above ground portion is straight. Even if it isn't all the way straight, the plant will adjust itself later.
When planting this way, you can't even tell the tomato plant was too tall when you're finished. Look at how much taller the plants are in the cell pack than the one that from that same pack that was planted with the trench method.
Just be careful not to bend it so far that you snap it in two! Also, when watering it early on, remember where you buried the root ball portion on the plant.