http://drupal.org/project/xtracker has what appears to be a drop-in replacement for the regular tracker module, currently visible at http://www.43folders.com/tracker. It allows people to filter out particular tracker entries that are uninteresting (like usernode creation), perhaps making it easier to keep up with new replies, new topics, and new blog posts? Or to just keep up with people signing up without having to wade through a bunch of post entries?