A Dictionary of Units
   A summary of most of the units of measurement to be found in use around the world today (and a few of historical interest), together with the appropriate conversion factors needed to change them into a standard unit.
   http://www.ex.ac.uk/cimt/dictunit/dictunit.htm

Apples4theteacher.com
   Measure the teddy bears game.
   http://www.apples4theteacher.com/measure.html

Conversion Calculator
   A simple calculator to convert between various units.
   http://www.thehaws.org/convert.shtml

Convert-me.Com
   Interactive calculators for many common and exotic measurement systems, including metric, Ancient Greek, Roman, and old Russian.
   http://www.convert-me.com/en/

CyberSleuth: Units of Measurements Worksheets
   Twenty-three printable worksheets for elementary school-aged children. Focuses primarily on conversion of units of length.
   http://cybersleuth-kids.com/sleuth/Math/Math_Worksheets/Units_of_Measurement/

FAQ: How do I read a ruler?
   Instructions on how to use metric and English rulers.
   http://www.onlineconversion.com/faq_05.htm

Funbrain.com
   Measurement game - Game which has several levels of difficulty for both English and metric rulers.
   http://www.funbrain.com/measure/

GCSE Maths: Measurement
   Includes length, area and volume and the use of prefixes in units. With worked examples and animations.
   http://www.gcse.com/maths/measurement.htm

How Many?
   A dictionary of units of measurement: explanations of the metric system, System Internationale (SI), English customary system, and other modern measuring systems. Plus extensive links to other measurement-related Internet resources.
   http://www.unc.edu/~rowlett/units/index.html

How To Read A Ruler
   Article describes all of those little lines and markings.
   http://www.woodzone.com/articles/Read_A_Ruler.htm

Jack's Math
   Provides several methods for determining length, width and height.
   http://www.nps.gov/whmi/educate/ortrtg/11or1.htm

Learning About Time
   History and description of clocks with lessons on telling the time. Includes an interactive tutor. [Requires Java]
   http://arcytech.org/java/clock/

Measurement Worksheets
   Features printable worksheets. Includes English and Metric System pages.
   http://www.edhelper.com/measurement.htm

Measuring Angle and Distance with your Thumb
   How to use body parts to estimate measurements.
   http://www.vendian.org/mncharity/dir3/bodyruler_angle/

Metric 4 US
   A site promoting the metric system which argues why metric is better and English is worse. Provides an English-metric online calculator.
   http://www.metric4us.com/

Metric Conversion
   Java metric conversion calculator for length, weight, pressure, and volume.
   http://www.worldwidemetric.com/metcal.htm

Metric Conversion Chart
   Online metric conversion calculator includes metric, US customary and Imperial unit conversions.
   http://www.sciencemadesimple.com/conversions.html

Metric Conversion Tables
   Conversion factors and online calculators for metric and imperial units.
   http://www.metric-conversion-tables.com/

Metric Measures
   Offers equivalents for common measurements, plus how metric units are used in sports and the kitchen.
   http://www.nist.gov/public_affairs/kids/metric.htm

Online Units Conversion
   Gives equal values for areas, volumes, circle measurements, computer storage, currencies, distance and length, energy, fuel consumption, power, pressure, speed, temperature, time, torque, and weights.
   http://convertplus.com/

Origins of Measurements
   Compares units of ancient times with modern ones.
   http://www.iofm.net/community/kidscorner/maths/origin.htm

Percent Change Calculator
   Measures the difference in values using percentages. Includes bar graphs with the answer.
   http://www.percent-change.com/

Temperature Converter Fahrenheit Celsius (Centigrade)
   A temperature converter for Celsius and Fahrenheit.
   http://www.albireo.ch/temperatureconverter/

The Modern Metric System
   Dictionary of metric units explaining the principles and history of the system.
   http://web8.ehost-services.com/cdkaese/metre/

The Ruler Game
   Timed game will test how quick you can read a ruler.
   http://www.rickyspears.com/rulergame/

Unit Conversions
   Online conversions from physics units to other physics units. Includes a comprehensive set of units with definitions.
   http://www.chemie.de/tools/units.php3?language=e