I just learned about donorschoose.org this week. It's a website where teachers can go online and post a description of a project they need funding for (large or small), a description of their school/students and it matches their need to a prospective donor. Donors can donate to all or part of a project.
I funded science materials for a charter middle school in Colorado. It was easy to do and I picked the project and the amount I donated. Check it out!