I'm stuck with a crappy digital signage platform that only renders .html and .swf files (and RSS feeds).No customization of RSS, only way to show something dynamic in a pretty way is to use Flash.The question: is there any way to embed JavaScript in .swf files or somehow have Facebook and Twitter Flash plugins?I looked for ready-made .swf widgets for the job but didn't find any, if there is any Flash widget that serves a Facebook and/or Twitter feed please give me a link.
Flash Twitter and Facebook widgets
flash
You really cannot load complex JavaScript into Flash. It will not work. You said your signage app supports RSS. One simple option is to create RSS feeds from the data you are trying to get from Facebook or Twitter. You can use PHP, Asp or something else to gain access to the Facebook/Twitter APIs. Then  create dynamic RSS feeds that Flash can read. Flash can also read XML that is more complex than RSS. This gives you a lot of options.I know Facebook has an ActionScript 3 version of their SDK. You can also use that SDK to build on the Facebook platform (http://code.google.com/p/facebook-actionscript-api/).  This might be a bit too much for a digital signage application where I am assuming you just want to show live updates?