I work with a social enterprise called The Extraordinaries. We just created an online volunteering platform called Sparked (http://www.sparked.com), which allows skilled folks like yourselves to volunteer for nonprofits around the world, all through the web, and in just a few minutes at a time. Many of our nonprofits are in need of simple creative help - website feedback, logos, twitter backgrounds, etc - which is why I'm putting a call out here.
It would great if you all could sign on as individuals. But it would be even greater you could get your entire design firms involved. If your whole team wants to jump on board, gimme a holler - firstname.lastname@example.org.
Meanwhile, check our platform out @ http://www.sparked.com and tell us all what you think!