Flash - The best thing out there actually.
Actually the only plugin aside of Unity which I consider "The best thing happened" to Web is Flash.
Flash offer today the best web based game performance/ Video streaming / Quality of product and Enterprise class Web applications - based on Flex Framework.
Checking on mobiles - Adobe Flash - AS3 is the REAL CROSS-PLATFORM Single codebase with high performance, same looking - Code Once - run everywhere programming language out there.
It is run on all current devices, all browsers, and it is capable of running on practically everything where Quality, Performance and Great Look means something.
Adobe Flash is actually THE ONLY CUTTING EDGE PLATFORM currently available worldwide.
I am strongly behind Microsoft for union with it on all of it's products. Because Microsoft is targeting the same targets with Windows. Go Microsoft! Adobe is the way! :)