Back in the days of Flex Builder 3.0, Adobe has bundled an offline reference for ActionScript and Flex framework API. The reference is more than just an HTML documentation as it provided a nice outline view of all the packages, classes as well as method and properties. Starting Flash Builder 4.0, such feature has gone away.
Doc? has come and filled the void, and it does more than just providing references for Flex framework. It is a parser that parses through online/offline ActionScript documentations, index and store the documentations in local database, which is extremely useful as I collect a bunch of open-source libraries, and the documentations come in handy.
So hit the link and give the program a try. Don’t forget to send the project donation (or beer 😉 ) if you find it cooler than I say in the blog.