Virtual Manipulatives
These sites contain excellent resources to develop within the student the ability to visualize, conceptualize, reason, and problem solve.
Ambleside Primary School (check back)
Educational Development Center in Maine: GeoGebra Applets
Johnnie's Math Page - Math games and activities for several math areas
Khan Academy - Math resource videos to teach almost every subject K-12
Math Games (some made by students)
MISTM: Maine's Impact Study of Technology in Math
National Library of Virtual Manipulatives
NCTM Illuminations Online Activities
Oswego School District Mathematics Resources Create your own interactive games)
Teaching Middle and High School Number Concepts