Sounds like your tomatoes are spaced between 8 and 12 inches apart, which should be fine.  As the plants get larger leaves and fruit can touch, you just don't want the roots to be cramped for space.

Make sure they get plenty of water, morning sun, are fed once or twice a month (preferably with something organic like worm tea so you don't "burn" your plants with the chemical stuff or deplete the good microbes in the soil), and are well supported with either stakes or some other support system.  Whether you have your own fertilizer or store bought, I have heard that crushed egg shells works well to feed calcium to tomato plants.  Also, when the plant gets 3-4 ft tall, I believe you are supposed to cut the top off to encourage growth horizontally and fruiting (i've never done this, but have heard it increases yield and will try this year).

My cherry tomato plants are going strong...should be ready for salads next week!  Good luck and enjoy!