MIT Biology Hypertextbook: Prokaryotic Gene Regulation:
http://esg-www.mit.edu:8001/esgbio/pge/intro.html

Faculty page on nitrogen fixation:
http://web.reed.edu/academic/departments/biology/nitrogen/

CDC information on cholera:
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/cholera_g.htm

lac operon animations:
http://www.leeds.ac.uk/bionet/compend/bnt28pst.htm

Attenuation Within the Tryptophan and Phenalanine Operons:
http://members.aye.net/~jfbaker/atten.html