http://eduref.org

This is a site that I'll keep as a reference, primarily because someone else has already invested a lot of time and effort in searching out and cataloguing other sites that I most likely might need at some point in the future. The categories and organization of the site is clear and logical. It's not the type of site one can completely explore in a short time, but that's not really its function. It's meant to be a resource to use when the need arises. A good site to bookmark.