Images of bioluminescence: from the Harbor Branch Oceanographic Image Library.
Jeff T. Alu: mostly greyscale, somewhat abstract landscapes; prints available.
Library of Underwater Images by John Petrak: Extensive, high quality, and well organized.
Jørn Tompter: Many pointless portraits of boring people and pictures of walls painted with pictures, but there are few strongly original compositions here that make it worth a visit. The site is entirely in Flash.
The Gigapxl Project: “Defining the upper limits of large-format photography [...] The Project's near-term goal is to compile a coast-to-coast portrait of America”.
Liquid Sculpture: High-speed images of splashes.
James Duncan Davidson has some useful articles about photographic techinques and tools.
Viewfinder: “[...] a novel method for users to spatially situate [...] their photographs, and then to view these photographs, along with others, as perfectly aligned overlays in a 3D world model such as Google Earth.” Visit the link for an impressive video, and read the brief article in the NYT.
The Histogram as the Image: cleverly hiding the “real” image as the histogram of a gif file.
Wayne Yoshida: Notes on equipment and film. His description of the problems with rendering shadowed flesh tones on the Epson 750 are precisely what I've encountered with this otherwise excellent printer.
Sense and Sensors in Digital Photography: A very interesting article by Charles Maurer full of good sense on the subjects of resolution, sensors, lenses, and more.
Here are some practical notes by Charles Maurer on color matching for digital photography, published 4 Oct. 2004.
KenRockwell: No-nonsense assesments of equipment.
Small Flashes used Creatively: A series of tutorial articles.