HTML5 & Flash

Gameboy:

http://www.grantgalitz.org/gameboy/

http://www.codebase.es/jsgb/

NES:

http://benfirshman.com/projects/jsnes/

http://zelex.net/nezulator/

Windows:

http://www.michaelv.org/

iPad:

http://alexw.me/ipad2/

Got some? Recommend to html5 at tomasdev.com.ar ;)