My popular Subscribe to Comments plugin has now been enabled on the millions of WordPress.com blogs! Subscribe to Comments puts a checkbox in your comments form that, if checked when leaving a comment, will e-mail that commenter all followup comments on that post.
Give it a try! It’s a really simple and easy way to stay involved with a comment thread and actually have a conversation, instead of making what I call “drive-by comments.” Remember that you can unsubscribe at any time.
For people with their own WordPress installs, I’ll have an update to the plugin out soon, and may follow that with another if Donncha gets me the changes made to the WordPress.com version and I think the general WordPress community would benefit from those changes.