I stumbled across this very interesting list of 18 firsts on the Internet. It's a good way to look at things. You could argue who invented what first, and you often get nowhere that way, because "invention" is such a poorly understood concept. Everyone's work builds on other people's. The guy who invented the car used a lot of other people's work to create something with four wheels and an engine. Did it have to have a steering wheel to be a car? We could argue about that, and that would change who the inventor was.
Who wrote the first blog post? They give credit for that to Justin Hall (and mis-spell his name).
I wrote in the About page for weblogs.com that the first blog was also the first website. TBL's info.cern.ch was a reverse-chronologic list of new websites. That's how central to the web I think blogs are. But if that wasn't the first blog, let's see Hall's first post, and decide if that really was the first one.
Who had the first feed? That's going to be an interesting debate for sure. I can show you mine, it was first published on December 15, 1997. But what makes something a feed? Can you have a feed with no aggregator? Is it the aggregator that makes something a feed? If so, we'll have to figure out who wrote the first aggregator and when, and what feed(s) it read.
One of the criteria for being "first" is, imho -- Did your work lead to other people imitating you? That test says whether or not your work commercialized or popularized the concept. The implies "hitting the spot" where being the only one seems, somehow, less significant. That's one argument against Hall as the first blogger, but in favor of TBL. As far as I know there were no bloggers that formed a community in the aftermath of his Links from the Underground.
Pretty sure the first blogging community, in the sense that we think of blogging today, was formed around Scripting News. Most blogs today can trace their roots back to Scripting News, if you go back far enough. I suppose some communities are disjoint. Did LiveJournal spawn out of a blog that spawned out of something that came from Scripting? I have no idea. But I do know that most of the early bloggers were readers of this site, and many participated in the discussion group here. There was a website that traced the lineage, called BlogTree, and it verified that the root of the tree was Scripting News. This is something I'm proud of, I think justifiably.
One of the reasons I'm proud of it is that blogging was created without the lock-in you see in systems like Twitter, Facebook and though they'll argue for sure, Buzz. Even Posterous, Tumblr and Wordpress.com don't give you easy ways off their servers. Blogging started without the concept of a single server, so there was no place to get off of. The whole point was to be as distributed as the web itself, to give people independence, to let billions of websites bloom. This is such an obvious feature of blogs that people don't usually see it. But it's there, and it's hugely important.