Add this nesmaps.com to your awesome list. They have entire screen shots of popular NES games for your enjoyment. The above image is Contras first level.

A few awesome maps:

http://nesmaps.com/maps/MarioBros/MarioBros.html
http://nesmaps.com/maps/MegaMan2/MegaMan2.html
http://nesmaps.com/maps/Zelda2/Zelda2.html

Awesome to see what people can do with retro games.