Game Icons has a collection of many hundreds of icons for making game components: rules, game cards, game pieces, counters, markers, cheat sheets and so forth. I intend to visit this site on a regular basis.
James Ernest has written an interesting blog post on how the early Cheapass games were produced.
Cardmaker is a tool for using CSV files to easily generate cards for your games.
Lately, I’ve taken to making cards for units in my games, rather than putting it on on sheets of paper. Having the cards cuts down on table clutter and makes it easier for players to find exactly which unit info they need.
CardBoard is an interesting project. It’s a bit of software that simulates a deck of cards in a digital playspace, and allows you to play with friends over a local area network. Keep an eye on this one, because remote playing via the internet is sure to come.