A new cheap piece of downloadable content for Magicka is available on Steam. The $1 "Nippon" DLC grants you a Kimono robe, a Katana that can cut through armor, and a Bamboo Staff that adds resistance to all elements.
Until June 5, fifty percent of the proceeds will go to the Japan Relief Support program. On top of that, buying the DLC before the deadline date will also net you a spiffy new hat for Team Fortress 2: the Demoman's Conjurer's Cowl.
If you're looking for other ways to contribute to Japanese relief efforts, check out Play for Japan. The organization recently hit over $120,000 raised, and is currently getting ready to release a charity album.