Catholic Encyclopedia: Pythagoras and Pythagoreanism

Entry by William Turner. Concise summary of doctrines attributed to Pythagoras.
http://www.newadvent.org/cathen/12587b.htm

The Mystica: Pythagoreanism

Digest of this school's teachings and its relation to Platonism.
http://www.themystica.com/mystica/articles/p/pythagoreanism.html

Pythagoreanism

Information about the arguments in this book written by Eric Steinhart, including overview and chapter abstracts. Interprets "pythagoreanism" in modern terms, as a philosophy radically opposed to Platonism.
http://www.wpunj.edu/cohss/philosophy/faculty/esteinha/PYTHAG.HTM

Pythagoreanism

Detailed essay on the development and legacy of this school.
http://cyberspacei.com/jesusi/inlight/philosophy/western/Pythagoreanism.htm