The Educator's Reference Desk
Created by the same people who developed AskEric, The Educator's Reference Desk is a clearinghouse of information and resources for teachers. This service provides access to AskEric resources, including lesson plans and other online information about education.

MarcoPolo
A partnership of seven educational organizations that offers lesson plans, links to top web sites, search engines that help find needed information quickly, and supplemental resources covering geography, science, the arts, economics, the humanities, and mathematics.

Tile.net
A comprehensive list of listservs, usenet newsgroups, and ftp sites. Great for communicating with others around the world who share your interest in a particular subject.