As a personal project, I wanted to put together a parser for VAST responses. So I created an ActionScript library on BitBucket. It’s basic but takes care of the monotonous XML to AS3 mappings. It also allows for custom extension parsers. Check it out here: https://bitbucket.org/nathan.hinish/as3-vastlib
[UPDATE: URL is now https://bitbucket.org/nathan.hinish/as3-iablib]