http://www.donorschoose.org/homepage/main.html?z

DonorsChoose.org is a simple way to provide students in need with resources that our public schools often lack. At this not-for-profit web site, teachers submit project proposals for materials or experiences their students need to learn. These ideas become classroom reality when concerned individuals, whom we call Citizen Philanthropists, choose projects to fund.

Proposals range from "Magical Math Centers" ($200) to "Big Book Bonanza" ($320), to "Cooking Across the Curriculum" ($1,100). Any individual can search such proposals by areas of interest, learn about classroom needs, and choose to fund the project(s) they find most compelling.  Donations can be as little as $1.