If you haven’t still heard Mozilla Foundation is developing a new plugin that aims to be a Subtitute Adobe Flash (alternative) called Shumway.
Shumway renders flash content through translation of objects in flash file (SWF) while being red in HTML5 elements and ActionScript-code to JavaScript code. This week Shumway was added to testing release of Firefox (Nightly) build, unfortunately still the supported OS-es are Windows Vista, Win 7 / 8 and Mac OS X, Still there is no port for Linux and NetBSD / FreeBSD. At the moment those who run Linux / *NIX and want good flash alternative should check out Gnash – https://www.gnu.org/software/gnash/. At present time Gnash (Gnu Flash) is supporting almost all Adobe Flash v7, v8, v9, Flash v10 and newer is still not supported.