[miketwalker]

I know that most teams usually put sponsor logos on the front and/or back of their team shirts. If you have several small sponsors, there's usually enough room on the back of the shirt to throw in a small sponsor logo for each as a thank you. That's also nice because if you give team shirts to sponsors and all they see the free advertising they get out've it and it's just a nice thank you back to them.

Also, you could probably place sponsors on team banners or maybe a small display in the pits. If your team has a website, having a "Thank you" section towards sponsors is also a very nice visible way to give a thanks that anyone can see.