Wikipedia has some entries worth reading -

• http://en.wikipedia.org/wiki/Photography

• note particularly the antecedents to the "fixed" image - camera obscura and camera lucida - [link] and [link]

http://luminous-landscape.com/ - a wide range of essays and information on analogue and digital photography

http://www.apug.org/ - Analog Photography Users Group - for those who love the traditional technology

http://www.daguerre.org/ - one of my favorite media - the daguerreotype

http://www.alternativephotography.com/ - old and forgotten photographic processes

http://www.pinholeresource.com/select_images.html - lensless photography

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photo galleries

on the web have a look at http://www.photoblogs.org/ - a listing of photoblogs (mostly very clichéed and with little to say, though some have high production values)