OakSim
OakSim is a prototype front-end ARM assembler and Simulator that works entirely from within your browser!
Live web page here!
OakSim uses the assembler framework Keystone and the CPU emulator framework Unicorn which are both licensed under the GPLv2 license. These frameworks have been ported into a Javascript API Unicorn.js and Keystone.js via Emscripten by AlexAltea.