Follow The Math Forum
Drexel University’s Math Forum provides resources, materials, activities, person-to-person interactions, and educational products and services that enrich and support teaching and learning of mathematics. Its provides:
Encouraging communication: Through a growing collection of mailing lists, Web-based discussion areas, and ask-an-expert services, people (teachers, students, parents, researchers) can talk, reach others with similar interests, and find answers to burning questions.
Interactive projects: Volunteer “math doctors” and an archive help answer mathematics questions – see Ask Dr. Math. Questions about teaching and mathematics education may be sent to the Teacher2Teacher service. The Problems of the Week (PoWs) are non-routine mathematical challenges for students...something for all ages (even teachers). Also, take advantage of its section on Math Tools.
Math-related web resources: The Forum Internet Mathematics Library covers mathematics and mathematics education Web sites in depth, now linked to the Mathematical Sciences Digital Library (MathDL) which collects instructional material and commercial products, complete with editorial reviews, reader ratings and discussion groups.
The Math Forum has worked with teachers, students, and researchers to put the best of their materials on the Web, available via the Forum´s Teacher Exchange: Forum Web Units. Teachers are invited to contribute lessons.
If you have never been to this site, shame on you! It seems to appear as a relevant link on almost every mathematics term or issue I "google"...and it usually provides some helpful information.
Note: The above review is a revision of my original suggestion of this website on July 24, 2005. I felt the Math Forum website is significant enough to re-suggest it.