The nice people at the Web Security Research Group over at HP have created a bit of goodness that will find vulnerabilities in applications built on the Flash platform. Right now it's free but no doubt they will be merging this with WebInspect at some point I'm guessing.
It will;
(a) decompile the Flash application and extract the ActionScript code and statically analyse it, identifying things like information disclosure.
(b) reports on insecure programming and deployment practices and suggests solutions (like buy WebInspect? ;o))
(c) enables you to audit third party applications without requiring access to the source code.
All in all, a nice little addition to a penetration tester's web application testing toolkit.