Appleis AirPort menu item gives you quick access to the available WiFi networks near your Mac, but it lists those networks alphabetically. I think viewing the network list by signal strength makes more sense, and someone at Apple must agree.
To view WiFi networks by signal strength instead of alphabetically, simply hold down the Option key while you click the AirPort menu item. The list of networks will rearrange itself so that the strongest signal is at the top of the list and the weakest is at the bottom.
Standard AirPort menu (left) and sorted (right)
Unfortunately, there doesnit seem to be a way to make this the default view, but at least the Option-click feature is easy to remember.<!--#include virtual="/includes/newsite/series/quicktip.shtml"-->