Habitat Digitizer for ArcView 9 (National Center for Coastal Ocean Science)

Extension to aid digitizing habitat from georeferenced orthophotos and other data sets.

SpatialEcology.com

This site is home to a very good and sophisticated set of ArcGIS tools written by Hawthorne Beyer called Hawth’s Tools. You can download and install these tools in ArcGIS. The author has very good documentation on his web site. Some of the tools are basic (e.g., calculating area for polygons) and some are much more advanced.