Geek.com has a nice gallery of Atari 2600 game cartridge boxes and screenshots of what the games actually looked like.
Some might say that this practice "misleading". While I agree that to a modern eye, this art misrepresents what you are going to be playing, but it makes total sense when you look at the art in the context of the time it was released and try to understand how it was useful to gamers during this period.
Thanks, Sluggo!