Open Questions: Perception

Galaxy: Sensation and Perception: Categorized site directory. Entries usually include descriptive annotations.

Olfaction: "A tutorial on the sense of smell" by Tim Jacob. A very good, detailed overview of many aspects of the sense of smell. Includes some news of recent research and some external links. Additional information from the same source is here.
Olfaction: A more in-depth and technical survey of the sense of smell, by Leffingwell & Associates, a consultancy to the perfume and flavor industry.
More Common Questions about Synesthesia: Extensive list of questions and answers about synaesthesia, by V. S. Ramachandran and E. M. Hubbard.
Mechanisms of Sensation: A ScienceWeek "symposium" consisting of excerpts and summaries of articles from various sources.
Worlds of Feeling: November 2004 Scientific American sidebar, subtitled "Underappreciated yet vital, the sense of touch helps to complete an amazingly accurate mental picture of our surroundings and ourselves."
Bad brain wiring turns numbers into colours: April 2000 news article about synaesthesia.

Music and the Brain
Norman M. Weinberger
Scientific American, November 2004
Seeing Is Believing
Vilayanur S. Ramachandran; Diane Rogers-Ramachandran
Scientific American, January 2004
Hearing Colors, Tasting Shapes
Vilayanur S. Ramachandran; Edward M. Hubbard
Scientific American, May 2003, pp
Joined at the Senses
Bruce Bower
Science News, September 29, 2001, pp. 204-205: Some parts of the brain may handle more than one type of sensory information. This may indicate human senses are more closely related than usually supposed.
[References]
Vision and the Coding of Natural Images
Bruno A. Olshausen, David J. Field
American Scientist, May-June 2000, pp. 238-245: Statistical properties of features of the visual field make it possible for the visual system to efficiently encode images. Understanding this process in detail may lead to more efficient computer image compression techniques.
[Abstract and references]