Leeches - Photographs of various species from the North Pacific and the Ukraine. - http://www.univer.kharkov.ua/main/dep/biology/zoology/leech.htm
Hirudo medicinalis - Article about the medicinal leech from Animal Diversity Web. - http://animaldiversity.ummz.umich.edu/site/accounts/information/Hirudo_medicinalis.html
Hirudinea - An introduction to the biology, classification and ecology of leeches, the subclass Hirudinae - http://www.earthlife.net/inverts/hirundinae.html
Australian Museum: Leeches - A study of the behavior, biology, adaptation to habitat, feeding habits and importance to medicine, reveals leeches to be fascinating and extraordinary animals. - http://www.austmus.gov.au/factsheets/leeches.htm
About Leeches - The history of medicinal use of leeches. - http://www.frb.spb.ru/eng/leeches.htm
Class Hirudinea - Basic introduction to the orders and families, habitat, and value as an indicator of overall ecosystem health. - http://lakes.chebucto.org/ZOOBENTH/BENTHOS/xxvi.html
Leeches - Hirudinea - Photographs of members of representative taxa, and the equipment used in studying them. - http://www.vims.edu/env/research/leeches/leechfigs.html