Funny you should ask. http://xmlrpcflash.mattism.com/ is for AS 2. I converted it to AS3, fixed some bugs (maybe introduced new ones :), and it seems to work for me. I was going to seriously clean it up before annoucning, but since you ask, here:
http://www.hrum.org/people/debedb/pro/blog/2006/12/xmlrpc_in_flex_2actionscript_3.html
