Over the last few years several states have moved to honor Girl Scouting by producing "specialty plates", at an extra cost, for automobiles. 

This is usually the result of grass-roots campaigning to secure a set number of orders prior to the state agreeing to produce the specialty plate.

 
Sometimes the design is shown online, even though there was not enough orders to produce the actual plate.

Many images on this page come from David Miura's webpage http://www.angelfire.com/wy/gilwell/plates.html 

and are usedwith his permission. He has a lot more detailed information with some of the plates.