The Work of God's Children's Educational Project, a co-operative online venture that is developing a free public domain curriculum for home-educators. I came across it because of the collection of public domain images. This includes several hundred black and white images that are useful for newsletters, as well as a good collection of images of saints.
The main project is an excellent idea with a lot of potential to become a resource for families, whether homeschooling or not. The site uses wiki software to enable people to edit the pages and improve them.