NASA
Nasa Star Child: Dark Matter (Level 1)
This site provides a description of "dark matter" and how scientist study it.
NASA
Nasa Star Child: Dark Matter (Level 2)
This site provides a description of "dark matter" and how scientists study it. Vocabulary words linked to a glossary of terms, and a printable version are also available on the site.
BBC
Bbc: Dark Matter
A clear explanation of how dark matter was discovered and why it is important to astronomers.