FZip is an Actionscript 3 class library to load standard ZIP archives and extract/decompress contained files.
FZip parses ZIP archives progressively, allowing access to contained files while the archive is loading. http://codeazur.com.br/lab/fzip/
The potential for this is impressive, and they've already implimented it in ways I wouldn't've thought possible - an automatic .air file update checker. I'm not even sure there is a file format left that the ActionScript 3 trio can't manipulate...