There are several user-made Quick Reference cards for NetHack. Usually they are one or two A4 pages meant for printing out that list all the commands and possibly some other information.
|A guide to the basic controls of the game, by http://www.voehr.com/|
|A quick key command lookup, printable on one page.|
|A guide with info on the armor in the game. (File:NethackArmor.odt)|
|A guide with info on Scrolls and Amulets, useful for price-IDing. (File:ScrollsAmulets.odt)|