No, not the Dutch based football team, but a web technology recently becoming popular -
Ajax is an acronym for Asynchronous Javascript And Xml.
Ned Batchelder has a short summary on his site:
In case you aren't in the web design field, or have been living under a rock, there's this implementation technique called Ajax, an acronym for Asynchronous Javascript And Xml. Google Maps is its best-known showcase, providing a great fluid experience that does all sorts of things that sites like Mapquest and MSN Maps can't do (dragging, resizing, etc).
Now we have Ajaxian Blog, a blog devoted to all things Ajax. Basically, Ajax is inspiring a renaissance in the construction of web applications, and Ajaxian is helping to track it all.