Vanilla is cool forum software, and I do like the features in the "questions" plugin -- except for calling everything a "question" instead of a "discussion" or "post". Was very easy to change the PHP to bring some of that back though, nice.
Dion is awesome, but that little innocent blurb about "hey just use HTML to define your UI" at the end of the Ajaxian article has caused me some major sleep loss. The net result is joInterface, go check it out in the docs!