Bumper stickers are a literary form that seems to be going out of fashion (at least in Silicon Valley), even if you include the extremely compressed form of vanity license plates--which I do. My last bumper sticker became the last by virtue of having my car tail-ended on Embarcadero Road by another car whose driver was trying to read the fine print.
Like Haiku, the bumper sticker aims to convey something memorable or thought-provoking with a very few words.
I intend to publish here bumper stickers that I see or remember or imagine that stick in my mind.
Caveat: I certainly don't agree with all those I post; in fact, I find some of them offensive. (But not necessarily those that will offend any particular reader.)
I'd be happy to include contributions by others.