I made this chart with a custom font I'm developing. It's just about done and should be posted soon after a few tweaks, but I thought I'd show off a little first. This chart contains (to my knowledge) all of the major, minor, major seventh, seventh, and minor seventh chords that can be played open on the guitar (or at least all of the relatively easy ones), in standard tuning. It's most common to play the F as a barre chord instead of the one shown here, but it doesn't really belong to this table. Since there was an odd number of chords, I wanted to add another to make the table square. So I added an alternate G, which is the only alternate I know in this set (not counting things like adding base notes). It's not that common, though.
The chord diagrams are set in my new font, and the text is set in Linux Biolinum
Download to get the PDF version. Maybe you'll want to print this or something. It's always good to have a chord chart around.