Measurement Resources: Elementary School Lessons & Materials for Teachers
This website has a collection of resources for K-6 graders that are related to measurement. Sections include lessons on length, area and volume, metric units and conversion, and non-standard units and estimation, as well as more general resources. For example, from this page you can go to the "Ask Dr Math" section where you can find answers to tough questions. There are also a number of reference pages on various related topics and links to resources on other sites.
1, 2, 3, 4, 5, Kindergarten
The Math Forum