I'll expand a little more on this later, but I wanted to put it out there. A very compelling use of the blog format (and one I'm sure others have stumbled on already) is that of a 'Home Blog.' I've been keeping a running account of my family's household matters for ~4 months now (much longer than I've been doing this public blog.)
The categories on our home blog? Bear in mind, these are slanted toward our particular context, of being new homeowners, recently moved from a small apartment in San Francisco to a single-family home in Ohio. They are:
<Dog> (Name removed to protect anonymity)
Lawn & Garden
These could probably be tightened up a bit, but they've sufficed so far.
Most-used category so far? 'Customer Support' serves to track the constant and constantly grating conversations with Earthlink, credit card co.s, etc. etc. (Most entries are just infuriating accounts of how much time I spent on hold and the various half-truths, deflections and deferrments that I receive in lieu of answers.)
I've not yet had a customer-support issue rise to the level of Turbo-worthiness, but a couple have come close. These detailed logs give me real peace of mind, knowing that - apparently - the customer relationship records that I keep seem to be better than those of most of the companies that I deal with.
Oh, and suffice it to say that the blog is hosted on a local network only, with due security precautions taken. (For additional security, I generally don't post any salient, telling details on the blog -- no account numbers, passwords, names (other than customer service names, which I strongly suspect are made up anyway.))
Like I said, more on this later...