The Dojo Toolkit is a modular open source JavaScript library, designed to ease the rapid development of JavaScript or Ajax-based applications and web sites. InfoQ had a Q&A with Dylan Schiemann, CEO of SitePen and co-creator of the Dojo Toolkit, about AJAX, Comet, Bayeux, RIAs and the newly released Dojo Toolbox.
http://www.infoq.com/news/2008/07/dylan_schiemann_qna