Edit: Since my collection of wine cheat sheets is growing, I've added a label for them. See them all here.
I've been working on a follow-up to the article I recently posted about German Riesling, but between prepping for a new class I'll be teaching next year and deciding to hand-make some of my Christmas presents, that hasn't been finished yet! In the meantime, I thought I'd point out a few helpful wine infographics.
I love everything from De Long. (They have good Christmas gifts too.) Their Wine Grape Varietal Table is a great way to get familiar with the many grape varieties available, and does an excellent job of explaining each grape's flavor characteristics, acid and tannin levels, and in which wines and regions it's usually found. (I may hang this on the wall above my desk at home.)
I've recently discovered their Metro Wine Maps of California and France. These provide a great way to learn about the appellations of those regions, and the maps include info on the grapes as well as local landmarks. (The main thing keeping me from hanging the varietal table over my desk at home is that I can't decide if I'd rather have the French wine map.)
De Long also offers a handy vintage chart as a free pdf download in color or black and white. This one is small enough to fold up in your pocket and take with you to the wine shop. It covers all the years back to 1990.
Robert Parker offers a free vintage chart as well, but it's less visually appealing. However it does go all the way back to 1970.