Also see: EXIF Readers, Editors & Extraction Tools
From the About Graphics Software glossary, a complete definition of EXIF.
EXIF Metadata - Using Metadata in Your Workflow
From Digital Outback Photo: "Whenever you take a picture with a camera, or scan a slide, the firmware of your camera or your scanner captures not just the actual image itself, but also additional data, describing the environment in which the image was taken. This data is called metadata and its understanding and utilization can be an invaluable aid in your workflow."
This site is dedicated to EXIF and related resources. Offers a discussion forum, sample images, list of programs that use the EXIF standard, specifications, and proposals.
JPEG and Exif - Digital Camera File Formats
Digital cameras use a variation of the JPEG format called Exif that allows additional picture information to be stored with the image. This article from Ulead explains how to display and preserve this information.