I’ve just released a plugin I’ve been working on called “Sparkplug”. It’s quite simple (although some of the code turned out to be a lot more complex than I expected!), and just gives you a small sparkline graphic indicating the number of posts per day for the current “view”. This is particularly handy on multi-author blogs which are split up into discrete sections via category or tag.
It was specifically written for/tested on the as-yet-unreleased Prologue Projects theme from Automattic, so when that comes out, it’ll be ready to go. Check out all the details about Sparkplug.