Free Edition of the AGI GIS Dictionary  
   Nearly 1,000 GIS terms and 52 diagrams published by the Association for Geographic Information and the University of Edinburgh Department of Geography.
   http://www.geo.ed.ac.uk/agidict/welcome.html

About.com: Geography Glossary  
   Geographical terms defined.
   http://geography.about.com/education/scilife/geography/library/misc/blgg.htm

Geographic.org: Glossary  
   Alphabetized list of words with definitions.
   http://www.geographic.org/glossary.html

Biogeography Glossary  
   Terms arranged according to various subject categories including general biogeography, ecology, evolution, landscape ecology and taxonomy maintained by Radford University.
   http://www.runet.edu/%7Eswoodwar/CLASSES/GEOG235/glossary.html