Emscripten is an LLVM-to-JavaScript compiler. It takes LLVM bitcode (which can be generated from C/C++, using llvm-gcc or clang, or any other language that can be converted into LLVM) and compiles that into JavaScript, which can be run on the web (or anywhere else JavaScript can run).
Attractive Javascript plotting for jQuery
Guacamole is a pure HTML and JavaScript (AJAX) implementation of VNC. The current version is almost as responsive as a native VNC client, has full keyboard and mouse support, and should work in any browser supporting the HTML5 canvas tag.