3: xanga.com, deadjournals, fotolog.net (? not really a personal journal but might fit into another category for you), diaryland...

3. check http://www.diarist.net/registry/

The big example of category 1 I can think of is Slashdot. Also boingboing.net
For 2, look at the knitting community - very active and lots of members.
For 3, go to http://annarborisoverrated.com, and check out the various links to other blogs. http://commonmonkeyflower.net is an example of somebody who was actually playing around with their own homebrew journal software for a while. Come to think of it, lots knitters have their own blogs - for example, http://www.wendyknits.net/

Things I am not sure how to classify:
http://use.perl.org/
(sort of like LiveJournal, but for Perl programmers?)
http://www.planetpython.org/
(collects weblog postings by Python programmers)

Feel free to include my new blog, Baby Killbot.

For 1/2, the only one that comes to mind is Slashdot.

my words weblog is hosted by a portuguese blog server
http://blogs.sapo.pt
and it's at http://vertigo.blogs.sapo.pt
many portuguese weblogs, if you can understand them or have them translated, are quite complex & interesting, something i wasn't used to having been using english language blogs for a while.
one example:
http://universosdesfeitos.weblog.com.pt/
good luck with your search :)

Hmmm, I'm not sure, but a few personal journals that come to mind are:

Megnut
Kottke
Evhead
Wil Wheaton DOT NET (probably know of that one, if it hasn't been suggested yet)
Nubbin
Caterina.net
Matt Haughey's Whole Lotta Nothing

Those are just a few off the top of my head.

I tried a couple of knowledge-spreading LJ communities, [Bad username: homemade_fusion"] and earlier sw_rebroadcast but I think LJ is almost a dead medium for anything not personal.

Well, except for communities like Gearheads, Importracing, Macosx... there are a few.

dooce is a fairly well-known, terribly funny blogger. she's also lost her job as a direct result of what she's written there, so that's an interesting angle.

I suppose these kinda cover your 1st & 2nd categories:

http://www.thingsmagazine.net is absolutely fascinating.
http://www.eyebeam.org/reblog/ aggregates from various sources & often has guest bloggers.
http://spaceandculture.org/ Weblog for the journal Space and Culture, Sage Publications.

how about http://www.boingboing.net/ as an interesting combination between group personal blog and metablog.

Personal journals that aren't livejournals that I read daily that you may know of already, but well:

Heather Corinna: http://www.femmerotic.com/journal.html
Belle du Jour: http://belledejour-uk.blogspot.com/
Pussy Ranch: http://pussyranch.blogspot.com/index.html

(also, mine, http://www.sacredwhore.org/mobwhorelog/)

fark is a filter/linkblog.

For #1: Bookslut and ALDaily, and MonkeyFilter (a MetaFilter clone - major diff. is Monkey allows new users right now, while MeFi doesn't.)

For #2: When I was considering law school, I read JD2B a lot. Craftster includes a lot of tutorials, but also a lot of plain old look-what-I-made posts. Sometimes I read a blog about project management/project development, when I feel like slacking, but pretending I'm doing job-related reading: http://www.jrothman.com/weblog/blogger.html

Journal-type blogs I read:
Hasidic Rebel got some coverage in the Village Voice a while back - that's how I heard of it. It's great, and one of the things I really like about the blogging format - an excellent look at a lifestyle & culture I know absolutely nothing about, and never get exposed to (not since I moved away from my old Chicago neighborhood, anyway.)
Mark Driver recently started to use a blog format for his writing - he's mean and funny and a great writer.
Jim Behrle is a friend/regular of The Hippie's, organizes readings for a local bookstore and writes poetry. You will not get any of this from his blog, which is mostly crudely drawn cartoons and laments about involuntary celibacy. Also baseball. The guiding principle of the blog is that "Douchebag" is the best word in the English language. I find him very funny, but you may not.

WOMAN HOW DO YOU HAVE TIME TO SLEEP??

These are fantastic

Command Post - started in the run up to the war and now tracks all kind of news.

Technorati may be of interest

Personal Journals that are not LJs:

Margaret Cho's Blog eloquent, personal, profane, funny

Josh Marshall's Talking Points Memo the question here is when does a personal blog stop being a personal blog. He's a journalist after all, but this is not his column for the Washing Monthly.

1) Check out the

1. I guess these would kind of go in the first category, kind of in the second - they're blog link aggregators - basically, each has some sort of system whereby they find URLs to which multiple blogs are currently linking. The aggregator then posts the links, along with bits of context from each of the blog referrers. It's a nice way to catch up on what's making the rounds when you don't have time to wade through everyone's individual blog. Only problem is that each system is automated, so sometimes you miss the personal touch that comes with a weblog that is generated by a real live person with ideas. Anyways. I've used the word blog one too many times in one paragraph for my comfort.

blogdex - an MIT media lab project, basically anything and everything that multiple blogs link to
Popdex - basically same as above
Memeorandum - politically oriented versions of above, with bits of blog commentary included. Really interesting to see the way that partisan pundits group around certain stories in an "i-told-you-so" sort of fasion

the evilzug community on LJ would fit into your first category methinks.

www.typepad.com and www.blogspot.com are both personal non-lj blogs. My friends there are emmett.typepad.com and kosherpork.blogspot.com.

Some random thoughts I have had about LJ versus other blogs:
- software: LJ (and typepad or blogspot) do not require the user to install software and secure web hosting; many of the personal blog sites use something like Movable Type or homebrew software requiring a bit more tweaking from the user (hence the preponderance of teenage goths writing bad poetry on LJ? who knows?)
- the huge difference between LJ and other types of blogs is the existence of communities in LJ
- LJ communities seem to be functioning much like Usenet newsgroups of yore - better because you don't have the spam, worse because you don't have the hierarchical naming convention that quickly allows you to establish if a certain newsgroup or community catering to your interests already exists.

In group 1, there's the venerable robotwisdom and memepool.

I'm not sure exactly what you mean by knowledge blog... a deep focus on a particular subject by assumed experts on the subject? Like aint it cool news, mocoloco, or autoblog or lvartsandculture? Or blogs with a more academic taste, such as Nick Yee's Daedalus Project?

Looks like you've already been given a nice list of personal blogs and blogging systems...

And (here's my shameless promotion bit), what about the sort of weblogs that straddle all three?

aldaily.com has got to be my favorite "filter blog" ever

i have a personal journal that isn't a livejournal, with about seven years of archives. villanelle.org ;)