Send of a tweet with your location, or just tweet your latest location with Twiphlo. Twiphlo conveniently provides a way for users to also include a Google Maps link of their location in their tweet.
Twiphlo is a neat one-click location updater for Twitter. Twiphlo sports a neat and clean UI design, which is also conveniently iPhone optimized. However, most mobile web users should be able to access Twiphlo from their mobile web browsers.