Dave Winer’s simple explanation of blogging and OPML:

First, create a new weblog on one of the free services, like Blogger or MSN Spaces. It takes about five minutes, and is about as hard as creating an email address on Yahoo or Hotmail, and represents less of a commitment. Then make your first post, something like Hello There, or Testing 1-2-3. Once you’ve verified that it works, you can stop there.

Then someday, when you’re in the shower or lying in bed in the morning and get an idea that you wish you could tell everyone, remember that you have a blog, and go to the computer, and write it up and publish it. That actually feels pretty good, even if you think no one will read it, because you got it off your chest.

Then in a few days Google will probably visit your site and index the post, and then when someone searches for that subject, your page will come up, and maybe you’ll pass that idea on to someone who can use it, or meet someone who agrees, or someone who disagrees. And that’s blogging, and that’s all it is.

As for OPML:

Did you ever have an idea you wanted to post on your blog that didn’t seem big enough to be an essay? An idea that could be expressed in a sentence, or less, but still deserved to get out there? In writing school they teach that less is better. If you can say something in three words instead of twenty, say it in three. It communicates better. Well, none of the existing blogging tools can do little sentence or phrase-size blog posts.