National Council of Teachers of Mathematics
Nctm: The Math Forum
This is a useful site with lesson plans, problems of the month, etc.
Teachnology
Teachnology: Math Lesson Plans
Great lesson plans covering a wide-range of math-related subjects.
National Council of Teachers of Mathematics
The Math Forum: Using Geoboards in the Classroom
A thorough look at the extensive uses of geoboards in the classroom. Links are listed which give introductory information on geoboards - for teachers new to using them. Then, lesson plans are provided for using geoboards in teaching...
National Council of Teachers of Mathematics
Nctm: Standards for School Mathematics
This standards-based NCTM website offers resources for teachers of mathematics for all grade levels, including interactive math tools, lesson plans, online resources, and the like.
Other
Smart Math Worksheets: Math Worksheets
Cover a great deal of content with these downloadable worksheets. Topics include fractions, division, addition, numeration, geometry, subtraction, multiplication, integers, decimals and algebra.
Other
Math4children.com: Math Worksheets for Middle School
Download these math worksheets to assist you in the concept you are covering in your middle school math classroom. Content includes pre-algebra and algebraic equations, decimals, fractions, geometry, graphs and coordinates and...
George Mason University
Handmade Manipulative Instructions
At this personal site, you will find pages of math manipulatives and different types of graphing paper to print out and use in your classroom.