Installed Alex King’s Popularity Contest plugin. It keeps excellent stats for the admin on how popular each blog post is. It also shows users a list of the most popular posts by category, month, etc… in the sidebar.
I found this plugin via the Weblog Tools Collection plugin competition.
The front-end is nice and the back-end (what the admin sees) is beautiful.
I just threw $15 to Alex for this and other things he’s written that I use.