Muut (formerly Moot) is a lightweight, customizable commenting system. Octopress is a static blogging framework built on Jekyll. Mix the two and you have a delicious recipe enabling visitors to comment on static blog posts without having to resort to a database.
My Octopress plugin makes this integration super easy. Install the plugin, edit 2 files, and you’re off to the races. You can even control which blog posts can be commented on.
If you’ve never worked with Octopress before it’s well worth a look see. I use it on a couple of my blogs (The Teascript Blog and The Distance Learner) and have been very happy with the performance. Nothing beats static HTML for raw speed.