Jon Davis’s CacheFile, is a centeral place to store common libraries such as Dojo, jQuery, Ext, Prototype and more. Dojo has a nice CDN already thanks to AOL, and YUI thanks to Yahoo! The other libraries don't have the same, so this could be the solution:
CacheFile.net is an HTTP web server that contains common Internet resources that are frequently reused on other web sites. It exists to alleviate the need for a common root URL for web resources that are otherwise not directly linkable at their primary URLs.