Other
Bipm: The International System of Units (Si)
BIPM (Bureau International des Poids et Mesures) is an international organization, located in France, an equivalent of our National Institute of Standards and Technology (NIST). This site is the BIPM intro page to their official...
National Institute of Standards and Technology (NIST)
International System of Units: Si Base Units
This is the definitive source for information on SI base units, derived units, squares, cubes, luminosity, field strength and flux density.
Other
Bipm: Si Brochure
Here's where to obtain your official brochure on SI, from the people who derived it. Little info at this site, except how to order an official brochure (and its cost). Or you can download a copy free.
National Institute of Standards and Technology (NIST)
National Institute of Standards and Tech: Si Prefixes
The official prefixes adopted in the US, as stated by the National Institute of Standards and Technology. Yoctograms? Zeptosecond? Yes indeed.
National Institute of Standards and Technology (NIST)
Nist: Rules & Style Conventions for International System of Units (Si)
The official rules for using the SI (metric) system in the US, based on the National Institute of Standards. Must download their handbook.
Science and Mathematics Initiative for Learning Enhancement (SMILE)
Smile: Metric System
This lesson plan familiarizes pupils in grades 4-6 with using the metric system and performing conversions.
Other
Wfp Consulting: Si Navigator
A commercial site which has links to many SI/metrics sites. It gets you to a host of sites. Don't hesitate to use it for research.
National Institute of Standards and Technology (NIST)
International Systemn of Units (Si)
The official sources from which NIST forms its decisions for "official usage". Most useful if you're doing serious research about SI.