New to OS X 10.8.4 is a Wireless Diagnostics app, which you can access from the Wi-Fi menu extra in your menubar (press the Option key, click the Wi-Fi menu extra, then choose Open Wireless Diagnostics), or by double-clicking the app in /System/Library/CoreServices.
Apple provides information about this app, which generates an archive of log files for troubleshooting. Wireless Diagnostics also features a number of informational sections. After you've generated a log, a Summary screen offers you information about Wi-Fi Best Practices, and provides information about any issues you may have.
A Utilities window (accessible from the Window menu) provides more information about your Wi-Fi network. It lets you scan all available Wi-Fi networks, offers a performance log, and much more.
This is a powerful tool, which can be very helpful if you are having Wi-Fi problems.
[kirkmc adds: I found, after posting the hint, that this isn't new. It's been available at least since Mac OS X 10.7. I didn't find it when searching the site because it used to be called Wi-Fi Diagnostics. OS X 10.8.4 brings version 2 of the app, a "major revamp," according to my Macworld colleague Dan Frakes.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20130610040531262