Sorry about the short notice, but I just found out about Extra Life. It's a gaming marathon taking place today in support of the Children's Miracle Network. Teams select a hospital they wish to help, ask for sponsors who will donate to the cause, and then they game.
Check it out, and participate if you're so inclined by creating or joining a team. (If you choose to game, please take the advice on the site's safety notice page!) If you aren't up for marathon gaming, then consider supporting a team, such as, for example, the CBT Tankers.
For once, I will have to actually say something good about the G4 network: they are supporting Extra Life, and live streaming a sort of online telethon. Well done.