Learning Math: Measurement
http://www.learner.org/channel/courses/learningmath/measurement/index.html
The Annenberg Foundation and the Corporation for Public Broadcasting explores Measurement in ten sessions that include companion online videos. Learn about standard units in the metric and customary systems. Examine how measurement can illuminate mathematical concepts such as irrational numbers, properties of circles, and area and volume formulas.

 

Measurement
http://www.staff.vu.edu.au/mcaonline/units/measure.html
Study units of measurement and learn how to convert them into smaller and larger units. Find out how to calculate perimeter, area, and volume.

 

AAA Math: All About Measurements
http://www.aaamath.com/mea.html
Click on the links to learn more about time, length, mass, volume, and temperature. Each section includes an explanation and some interactive practice using conversion quizzes.

 

How Many? A Dictionary of Units of Measurement
http://www.unc.edu/~rowlett/units/
You probably could never guess how many words we use to talk about measuring! Click on any letter of the alphabet to find definitions for all types of measurement units including international and ancient measurement systems.

 

Metric Conversions.org
http://www.metric-conversions.org/
Automatically calculate metric measurements for length, distance, temperature, volume, weight, and area.

 

BONUS:
FunBrain.com
http://www.funbrain.com/measure/
Play using centimeters or inches and determine the length of the red bar.