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.
Apples4theteacher.com: Measure the teddy bears game.
Conversion Calculator: A simple calculator to convert between various units.
Convert-me.Com: Interactive calculators for many common and exotic measurement systems, including metric, Ancient Greek, Roman, and old Russian.
CyberSleuth: Units of Measurements Worksheets: Twenty-three printable worksheets for elementary school-aged children. Focuses primarily on conversion of units of length.
FAQ: How do I read a ruler?: Instructions on how to use metric and English rulers.
Funbrain.com: Measurement game - Game which has several levels of difficulty for both English and metric rulers.
GCSE Maths: Measurement: Includes length, area and volume and the use of prefixes in units. With worked examples and animations.
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.
How To Read A Ruler: Article describes all of those little lines and markings.
Jack's Math: Provides several methods for determining length, width and height.
Learning About Time: History and description of clocks with lessons on telling the time. Includes an interactive tutor. [Requires Java]
Measurement Worksheets: Features printable worksheets. Includes English and Metric System pages.
Measuring Angle and Distance with your Thumb: How to use body parts to estimate measurements.
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.
Metric Conversion: Java metric conversion calculator for length, weight, pressure, and volume.
Metric Conversion Chart: Online metric conversion calculator includes metric, US customary and Imperial unit conversions.
Metric Conversion Tables: Conversion factors and online calculators for metric and imperial units.
Metric Conversion Tutorial: Step-by-step, interactive tutorial for converting metric units.
Metric Measures: Offers equivalents for common measurements, plus how metric units are used in sports and the kitchen.
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.
Origins of Measurements: Compares units of ancient times with modern ones.
Temperature Converter Fahrenheit Celsius (Centigrade): A temperature converter for Celsius and Fahrenheit.
The Modern Metric System: Dictionary of metric units explaining the principles and history of the system.
The Ruler Game: Timed game will test how quick you can read a ruler.
Unit Conversions: Online conversions from physics units to other physics units. Includes a comprehensive set of units with definitions.