Mobile billboards are still something of an oddity here in North Dakota, but in other parts of the country they’re pretty common.  Basically, what they are is just a billboard attached to the back of a big truck of van which then drives around through major traffic areas so that pedestrians and other drivers see the ads.  They look something like this:

They seem like a fairly innovative way to advertise, but you wouldn’t think they’d be something the Sierra Club sent a big, fat SUV to escort Arianna “SUV’s SUPPORT THE TERRORISTS!!!” Huffington to and from one of their conventions.