jsMSX - The first MSX emulator 100% written in Javascript
http://jsmsxdemo.googlepages.com/jsmsx.html
"jsMSX is a MSX emulator 100% written in Javascript. Yes, you read it: Javascript! It emulates the underlying Z80 CPU, TMS9918 Video Display Processor (VDP), PPI, RAM slots and Megaram. In its present form, it should be able to run any program or game developed for MSX 1.0. "