University of Oregon
Ask Geo Man: Igneous Rock Forming Minerals
Ask GeoMan lists Olivine, Pyroxene, Amphibole, Feldspar, Mica and Quartz, as five common rock forming minerals. Characteristics of each are also given.
Other
Mindat: Feldspar
This website lists minerals included in the feldspar group, as well as some synonyms, relationships to other species, and related internet links.