The IP widget has been one of the most useful widgets I’ve installed on my Mac. It simply refreshes to your current IP address each time you refresh your dashboard. You can run more than one copy of this widget for your airport, ethernet, Firewire and Wan ip address.
If I’m joining a hot spot somewhere, I keep an eye on the widget for when I’ve been connected. Also, if I’m getting ready to grab a torrent with Transmission, I check to be sure I grabbed the ip that is forwarded through the router.
This is also a great widget to install on the dashboard of those unfamiliar with Mac OS X. It gives a fast way to find their IP address so you can connect with a VNC connection and troubleshoot their computer.
To sum it up, I use this widget a lot.