Just a thought regarding bumper stickers. You are right , most people do not like to put them on their vehicle, myself included.
How about the peel off variety, like the sticker they put on my windshield after every oil change. Point is it can be put on a vehicle window and then peeled off or transfered to another vehicle at will. Just the logo would be enough , making it a smaller sticker. People will ask what it stands for, and then we can make the pitch for the forum.
This forum is such a incredible resource and I appreciate all the administrators hard work. I would love to advertise for you with something beyond word of mouth.