Bridging AirPort Extreme Base Stations
A friend wrote in to ask whether the bridging feature in the new AirPort Extreme Base Stations -- which allows two to four of them to connect wireless and form a larger network -- works with the older graphite or snow Base Stations. Unfortunately, no. You must have Extreme units to get the bridging function at all.
There are options for adding bridging to existing networks or extending them, notably the Linksys WET11, which is a $100-odd device that looks like a client adapter to an access point, but it can stream all the traffic behind. We write about this in The Wireless Networking Starter Kit or you can read an article I wrote about it for O'Reilly Networks.