Some of these are simple hacks which use the Digg API, while others are full featured desktop applications. In any case, you have a wide selection to choose from; we've chosen 7 applications that we think are the best.
Digg Monitor - a plugin (trigger) for Proxi, a Mac application that "allows applications, system events, and devices to communicate with other applications, system events, and devices." Digg monitor will seek stories based on your criteria and show you how these stories are standing on Digg.
Social Site Submission Watch Dog A creative use of Yahoo Pipes from fellow blogger Engtech, which enables you to see how stories from your site are doing on Digg (i.e. it shows you the number of diggs for each story). Simple but gets the job done.
iGoogle Digg Monitor - just like the previous one, this tool also enables you to see how many diggs submissions from your site are having at any given time, but this one is in the form of iGoogle gadget.
Social Traffic Monitor - a Wordpress plugin that monitors your blog traffic and displays activity coming from Digg (or some other social news/bookmarking site). If your server isn't already down, of course.
DiggWatcher - a web based tool which enables you to paste the URL of any Digg story and see its stats, including the number of diggs and comments. Not the most beautiful tool out there but it gets the job done.
Digg Alerter - a standalone Windows program that resides your system tray and alerts you whenever stories that you submitted are dugg or promoted to the front page. It's a pity you can't monitor stories based on a keyword or URL.
DiggWatch - There are two applications named "DiggWatch". For the first one, you're going to need an older flavor of Apollo to run this one, which is not cool. However, this application was one of Digg's API contest finalists, and therefore we can expect an updated version in the future.
However, there's another DiggWatch, which is web based, and can be found here. It's a simple tool that enables you to track your comments, as well as comments of your friends on Digg. You can also track stories posted from a specific domain.