In just a day and a half, the massive virtual populations of Zynga's FarmVille, CityVille, and FrontierVille have donated more than $1 million in aid for victims of the natural disasters in Japan.
Zynga has added special virtual goods to several games which players can purchase to donate funds. It's a very clever use of in-game purchases, and one even the most jaded of FarmVille detractors can get behind. A button has also been added to Words With Friends to allow donations, and all Zynga's Facebook games will accept donations via its Zbar.
Even if you're not a FarmVille or CityVille player, you can still donate to relief efforts. Zynga and its partner Save The Children have set up a page where you can donate directly over at savethechildren.org.