Photo.Net
Probably the largest internet based community for photographers out there.
PhotoSig
Requires registration, not really for the casual user.
Fotosidan
Swedish Community
Digital Photography Review
Incredibly through reviews and a big forum to boot.
Luminous Landscape
By the sometimes controversial Michael H. Reichmann.
Rob Galbraith
Another of those really through review sites.
Steves Digicams
Another usefull site for reviews.
PhotoNotes
Great articles, take a look at the Canon Flash Photography. Its like the bible.
Camerans
Nice site with a incredible amount of links for various photography related things.
Schildt - Fine Art Photography
Unconventional, this is a must see.
Motljus.Com
Great photography site, mostly nature in its various forms.
Custom Hyperfocal Distance Chart