This website I thought was awesome because it covered most math topics in a fun way. There are games and puzzles for kids, and there is even a teacher section where there are teaching ideas and lessons. Also there is parent section with ideas for helping their kids and other suggestions.
This site has searchable video cases of real elementary math lessons teaching standards based mathematics lessons. You can also see a complete lesson plan with handouts.
The NCTM website has excellent ideas for lesson plans, interactive on-line math activities, challenge problems, and more. NCTM offers many professional development resources such as journals, on-line conferences, information about regional conferences, an
Highly respected site with great resource for teaching internet safety particularly for middle school and high school students. Divided into short units which must be done in sequence. Includes short videos for classroom use.