Microsoft Research has released a freely-downloadable version of their Social Network and Relationship Finder, more affectionately known as SNARF. I've been running an internal build for the past week or so, and I've found it to be very useful, especially if you send and receive a lot of e-mail (see Slaves to E-Mail?). As described by Rob Knies, SNARF "simply counts e-mails, sorts them by sender, and draws conclusions about their relative importance from the intensity of the correspondence relationship." A few views are displayed by default, my favorite being the view that shows recently received e-mail where I am on the To: or CC: line sorted by the inferred social significance of my relationship with the sender. It's a very quick way to see if you have unread messages from people you tend to communicate with frequently. It's already improved the efficiency of my e-mail triage process. Check out the SNARF Guide for some screenshots (the Thread View is handy).