I had a client request an AJAX loader be used on a Flash site that had, up to that point, been written in compiler-agnostic ActionScript 3. The requirements were not complex, as the animation was not expected to coincide with the loading progress. I immediately turned to the best resource on the web for AJAX loaders - Ajaxload.
Ajaxload is a great resource for royalty-free AJAX loading animations, and fit the bill perfectly. There's just one problem: animated gifs don't work in AS3.