Dark Matter Mystery - Takes a look at the candidates for dark matter including MACHOS, WIMPS, and gas.
MACHO Project - Primary aim is to test the hypothesis that a significant fraction of the dark matter in the halo of the Milky Way is made up of objects like brown dwarfs or planets, known as MACHOs, for MAssive Compact Halo Objects.
Wikipedia: Dark Matter - Article about the matter that can't be detected by its emitted radiation but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies.
