I learned of this through Fear the Boot, my favorite gaming podcast.
DriveThruRPG is offering a huge deal through the rest of January called Gamers Help Haiti. By donating $20 (which will go to Doctors Without Borders), you will receive a free bundle of PDF gaming material worth over $1000, including the Serenity RPG and the Cortex RPG System book (the system Serenity uses), Chronica Feudalis, Dork Covenant (the first Dork Tower comic collection), and a bunch of other cool-looking stuff.
So far they've raised $93,560 to help Haiti. Pretty sweet!