Apple has released a couple of knowledge base articles that offer information about the new AirPort menu as well as cover a problem people are having in which OS X 10.6 does not recognize iPhones or iPod Touches.
This article covers information about the new AirPort menu. The menu contains new icons and graphical depictions of network status, and these are explained here. I am quite relieved to see the signal strength displayed for each discovered network. I have used widgets and other applications for that in the past, and it is good to see Apple add this to the menu, along with the other features discussed in the knowledge base article.
This article covers a problem where if you installed the iPhone/iPod Touch software development kit in OS X 10.5, and then upgraded to 10.6, your iPhone may not be recognized by the system. Apple has a small compatibility update for the software development kit, which should be available through Software Update; however, you can probably also download and reinstall the latest SDK for the iPhone from the developer connection site: http://developer.apple.com/iphone/