DonorsChoose.org is kind of like microfinance for school projects. A teacher puts up a project that needs some funding, and we can all kick in a few dollars at a time to help some kids out.
I've put together a page and have had some success getting a number of projects funded, many being a high poverty area school in South Carolina. (Hey, do you hear me Stephen Colbert? That's in your home state. Oh yeah, you're on the DonorsChoose board… but I digress.)