Some of the biggest (most visible, longest lasting) blogs are collaboratively edited ones.
Slashdot is kind of the granddaddy. It started out as some dorks collection of technology news, and it turned into a large community of tech dorks all complaining about how Internet Explorer has some sort of component that magically compromises your morals as soon as you use it.
Slashdot is archetypal: stories are submitted by readers, then "edited" by the "editors," then posted on the main page, and then discussed and dissected in the forums.
Then there's
fark, an aggregator for news-of-the-weird type stories, as well as those common sense outrage stories that make so much damn hay. ("My tax dollars are going to pay for an art display that includes dildos?!?!") Fark's comment section is mostly just distilled idiocy but it makes some interesting contributions to the online lexicon at least (they really helped"asshat" get off the ground)
Plastic is what happened when
Suck died. Does anyone even remember suck? It was awesome.
Anyway, plastic runs in much the same way as slashdot, but it has a broader field of subject matter and it's readers, while still able of horrendous acts of non sequitur and ad hominem, are generally quite good at dissection and analysis.
Metafilter is a lot like plastic. Except aesthetically uglier.
BoingBoing doesn't do a lot of commentary, but it really is an exemplary model of how a team edited blog should be run. Plus, Mark Frauenfelder went to Boulder High School. I guess that's just trivia. I just like their subject matter. Copyright idiocy, counter culture, out-there media theory (lots of recent stuff on Douglas Rushkoff), stuff from Japan, cool devices, DIY...&c.
Drawn covers all types of illustration. I never knew there were so many illustrators with amazing portfolios on the web until I started reading drawn.
Popgadget is a female run gadget and tech blog, which is cool. Once you start reading a female perspective, you start to realize how this sort of stuff is normally seen from (and directed to) a male audience. A dirty, stinky, cheetos eating male audience.
Treehugger is really something else. It covers new design with a specifically ecological slant. It's edited and contributed to from everywhere. It's cool.
PS. I almost forgot
memepool. How I could do that I don't know. It's kind of a collection fo the wierdest, most esoteric, half-baked stuff to make it onto the web.