Photography Tutorials

Digital Photography Tutorial	This site offers ideas to make better photos.
Photography Composition Articles	Lots of articles from many different sources.
Photography section from the Guardian Newspaper website	This includes the "Guardian Guide to Photography".
Photography section from the BBC website	This includes "How to take Good Photos" by Tom Ang. Note, however, that this site is not maintained. It was last updated in 2007.
Fodors: Focus on Travel Photography	Fairly basic, but still useful.
Photography Tips	Lots of interesting information.

Pinhole Photography

Pinhole Photography	A page about, well... pinholes. It contains links to several other sites about the subject. If you are interested in pinhole photography, you should also be aware of Justin Quinnell's site.
Online Schools: Guide to Pinhole Photography	Another page about pinholes. It also contains links to several other sites about the subject.

Photoshop Tutorials

photoshopessentials.com	An excellent set of tutorials. The description of blending modes is amongst the clearest I have found.
Adobe	Tips from the makers of Photoshop. They assume, of course, that you are running the latest version of the software.
Russel Brown	Russell Brown is a creative director at Adobe. He has sime interesting tips which are illustrated in Quicktime to make them easy to follow.
AbsoluteCross Photoshop Tutorials	Not a guide to the whole package, but a set of tutorials for particular skills such as "drop shadows" and "burnt-in text".

History

A History of Photography from its beginnings till the 1920s
Dating Old Photographs	An article giving lots of information and links about the dating of old photographs.
History of Canon Cameras	Canon's own virtual camera-history museum.