CyanoBase:  http://www.kazusa.or.jp/cyano/
Introduction to the Cyanobacteria:  http://www.ucmp.berkeley.edu/bacteria/cyanointro.html
The Cyanosite:  http://www-cyanosite.bio.purdue.edu/
The Microbial World:  Cyanobacteria:  http://helios.bto.ed.ac.uk/bto/microbes/cyano.htm
Tree of Life Website Project:  Cyanobacteria:  http://tolweb.org/tree?group=Cyanobacteria&contgroup=Eubacteria
Virtual Museum of Bacteria:  http://www.bacteriamuseum.org/species/cyanobacteria.shtml