This was discussed a while back too. It started as an Axiom window cling for vehicles, and went from there...
http://www.axiomaudio.com/boards/showthreaded.php?Cat=&Board=first&Number=69875&page=&view=&sb=&o=
It ended up pretty much down the path of people making their own signs (can't call them plaques since they are different than what you are talking about)...
I just know that if I got all of the plaques for the stuff that I plan to put up in home-made signs, it would cost me a small fortune, plus I would not be able to get a THX or Axiom one for sure...
Good idea though!
