http://www.nctm.org/about/default.aspx?id=166

This website looks like a winner for K-8 teachers, and maybe even Algebra 1 teachers, to assess where your students are.  Check it out!

http://mathassessments.mscenters.org/

Teachers trying to meet national science, technology, engineering, and mathematics (STEM) standards now have a new tool at their disposal--a free online library called TeachEngineering. A national collaborative effort involving eight universities and organizations, spearheaded by the University of Colorado at Boulder, the site provides teacher-tested, standards-based engineering content for K-12 teachers to use in science and math classrooms. Teachers can search for curriculum content based on a number of criteria, including keywords, grade levels, educational standards, and more. Clicking on one of the listed activities tells users how long the activity takes, what grade levels it's designed for, what educational standards the activity meets, and the details of the activity itself. TeachEngineering currently matches activities to most national standards, as well as those of four states: Colorado, Massachusetts, Oklahoma, and North Carolina. By the end of the year, project organizers expect to have the standards of all 50 states integrated into the site.

http://www.teachengineering.org/

Check it out!!  Test Prep--Valuable for both students and teachers as a great resource!

  http://www.number2.com/

This site is too cool to pass up.  I've looked at the tangram puzzle and the crossing the river one and they are SO cool!  You're going to love these, and so are your students!

http://pbskids.org/cyberchase/games.html

Don't forget  about ALL of the great websites offered in the MeL Internet -> Education -> Mathematics Education section of this site:

http://www.mel.lib.mi.us/

Hands-on Statistics Activities:

http://stat.cst.cmich.edu/statact

Real World Learning Objects

http://www.rwlo.org/ 

Data Sets

http://lib.stat.cmu.edu/DASL/

Great student games that reinforce graphing, etc. 

http://hotmath.com/games.html

Brain Breaks -- all subjects, K-6

http://www.emc.cmich.edu/