cars with ads on them

I've heard about the cars given away by certain companies with their
advertisements plastered all over the exterior. I remember seeing this on
the television news first. I'd like more information on them. A search on
google turns up dozens of companies claiming to have a list for sale with
the names of companies giving these cars away. I'm not going to pay someone
for information I'm pretty sure can be found on the web for free.

Does anyone know of such a list on the web, or of a certain company having
this promotion?

Thanks in advance.