I am a Nikon user and fan, so several sites mentioned here are Nikon oriented. Of course there are several other manufacturers making excellent cameras. I'll mention other references as well, but the emphasis will be on Nikon, mainly because it is the system I know the best. I am often active on international forums under the pseudonym "gugs". Among others on fredmiranda, nikonpassion, nikoncafe, nikonians.
This forum is one of
the best references on the web regarding Nikon gear: technical
questions about camera's, lenses, photography, technique... Super
friendly people, very competent, funny and some very experienced (and
sometimes famous) photographers - an excellent community.
Other subforums on Fred Miranda also share the openness and friendliness found in the Nikon forum, subjects include Macro, Landscape, Canon gear.
There is also a very interesting review
section, but not complete (some recent or very common lenses are not
always included) One of the best photography sites overall.
This site is a French site, for the French speaking Nikon fans. Also a lot of very friendly people, with quite a lot of film shooters. The best resource in that language. Lots of downloads (old documentations, interesting resources)
Also a nice Nikon site, very friendly people, a lot of subforums, about technique, cameras, lenses (lens lust), and a number of categories like landscape, night shooting etc... Some members are also members of Fred Miranda or other sites. A few very knowledgeable people are there if you have very specific technical questions.
This is a very general forum, less appreciated by the "real" photographers but that's just their reputation. Very valuable information and reviews about camera's, a really interesting resource about all brands and all levels of cameras. The forums and discussion are not always of the same level as the other sites (sometimes they are), people are not always as friendly as on Fred Miranda for instance, and sometimes endless non-sense discussions start.
Not perfect put definitely worth viewing. They have a nice newsletter you can subscribe to.
Another specialized forum, but not my
favourite (even if I have reservations, I only mention links that are
very good to excellent). Valuable information and some very
knowledgeable people but there is a rule not to post pics if you don't pay, making the whole experience less
interesting. The sub-forums are divided into camera types and that
makes the discussions a bit too specific (too many subforums to browse
if you want to collect general information). They have very interesting
reports (for instance comparing wide angle lenses or explaining the
D200 focus system) and that makes the site worth a visit. Their
resources are among the best on the net. They also have a nice shop
where they sell some accessories and nice "gadgets" (caps, t-shirts).
There are now better choice than
Nikonians on the net. Their information is still very valuable but I do not
post a lot anymore and don't have the intention to contribute very actively anymore. I
understand their position but their policy is too strict. They could
have found an intermediate solution. A pity looking at the quality of their reports and of some of their memebers.
Les Pixelistes
An excellent French forum, a bit similar to Nikon Cafe, lots
of categories, very friendly people (maybe too friendly when you want
to get a critique). They also organize contests with nice prizes. There
are lots of sub-forums with specific threads per camera or per lens. A
useful resource for French speaking people. Nikon users only.
Nature forum in
Benelux
A French speaking forum for
nature lovers (birding, mammals, landscape, etc...) Originally meant
for Belgium, all kinds of French speaking people do participate.
Birdpix
This site is a specialized site for birding, mainly Dutch speaking (it
is possible to interact in English, all members do speak English
too).
Nikonlovers
A French forum about Nikon digital equipment mainly very
similar to Les Pixelistes. As the name does NOT indicate, it is French
only.