There's an article in this month's Business 2.0 called "Blogging For Dollars", that mentions several popular sites like Tech Crunch and BoingBoing. BoingBoing, according to the article, is making about a million bucks per year in ad revenue. Doesn't sound like much, but it's just four people, and they all have other jobs and stuff. Not bad at all. The biggest surprise though has got to be Fark.com, which is apparently pulling down hundreds of thousands of dollars per month, despite a lack of original content.
The conventional wisdom is that successful blogs pic a very specific area (like camcorders) and focus on it with great energy. But sites like BoingBoing, Fark, and dooce.com certainly don't fit that mold.
V has finally started a blog that looks to turn into a wedding blog, so we'll see how that goes. I, meanwhile, am way too scattered to focus on a particular area.