I'm closing in on 1000 entries in this blog, so it's time to do a little bit of retrospective analysis and look at some of the tools I'm using to keep track of which parts of the site are unusually active well after the original post hit.
The more general term for this would be blog analytics. Here's some capsule reviews of some tools and an approach.
One theory of blog analytics is to identify the things that you're writing about that don't own page one for the queries that are being searched for, but which still are clicked on regularly by people who go a couple of pages deep in the listings. If it's good enough to look at on page two, write about it again until it shows up on page one. Tools like 103bees and Hit Tail are specifically focused on this task, and they have views into your analysis reports that show which pages are on page two (or even deeper) on search results. You can do the same thing by hand if you have raw server logs by looking for "start=20" or "start=30" in the referrers - those will be indicative of click-throughs from pages deeper in the search listings.
A second useful approach to seeing where your blog fits in the greater world is to focus on the postings that are getting hits months after the original. If you are using a typical chronologically arranged publishing tool these are pretty easy to pick out since the filenames often include year and even months. Find a perennial favorite and revisit the topic from time to time either with new insights or just with an update to what else is new around the net since you last wrote. (Thanks to Brian Kerr for this idea.)
A third technique for testing effectiveness of a blog as a way to focus people's attention on something else is to look through the logs to see where people went to after they visited your site. The mybloglog tool has pretty good reports and tools for doing that, both for reporting in real time what the most visited links are as well as collecting over time where the hot exit points are. Close the feedback loop here again by writing about things that people are actually clicking on at the moment.
You can, of course, get so enveloped in feedback that you never actually write anything. Sometimes you want to get as far away from what you've said before and think about something new, and I don't know anything better to give ideas for that than LibraryThing's Unsuggester tool. It doesn't actually work on blog postings directly, but there's nothing better to help mix up your writing than to contemplate two opposite works (Polya's How to Solve It vs The Devil Wears Prada) and come up with a synthesis of the two.