This may have been posted before at some point, but I just came across http://www.arcadeflyers.com/index.php?page=news
and its a great site with a ton of the old promo flyers scanned. It pretty funny how they are worded as a sales pitch, for example:
"Your codename for an outstanding investment" as a tagline for a Rolling Thunder flyer

They also have non-US/Europe flyers as well, pretty cool site