WonderFl allows you to write, compile, run and share ActionScript applications online. It has a decent library of projects to search through, and you can create a fork from an existing project to build on it.
Swiffy converts Flash SWF files to HTML5, allowing you to reuse Flash content on devices without a Flash player (such as iPhones and iPads). Swiffy currently supports a subset of SWF 8 and ActionScript 2.0, and the output works in all Webkit browsers such as Chrome and Mobile Safari