What did 37signals, Evernote and Wufoo blog when they just get started?

37signals blog (Signal vs Noise) precedes Basecamp by a couple of years, their first post is from December 2002, http://37signals.com/svn/archives/000001.php. It was a pretty popular blog by the time they launched Basecamp.

Joel on Software precedes FogBugz, if memory serves me well. StackOverflow precedes Coding Horror, of course. The lesson here is that building a reputation comes very handy when creating web apps.

I don't have much to contribute to this discussion myself, but from what I've heard/read, at the beginning, you should target other entrepreneurs/early adopters and when you get some coverage/traction, move to your target audience for your product.

PS: I'm really interested with what you guys have to say about that.

It depends what you are trying to achieve with a blog a bit to, are you trying to address customers, prospective customers primarily or are you trying to become an authority in your niche by writing about it more broadly and picking up a lot of search traffic. I think a great example for authority is SEOMoz, provides value well beyond the actual product.