The AirPort Mangement Utility and AirPort Client Monitor provide powerful tools for planning, setting up, fine-tuning, and managing larger, enterprise-class wireless networks.
This utility ran on older version of Mac OS X 10.3 and as the description above says can be used to manage your AirPort wireless networks.
Since this tool does not work on Snow Leopard I prefer to use iStumbler to troubleshoot wifi speeds etc. on my Macbook Pro.
Check out iStumbler here: http://www.istumbler.net