An emulator built with the EMF system, which aims to significantly lower the barrier to entry for emulation developers, and would-be emulation developers.
It does this by removing the complex code, providing instead a domain-specific language which describes the entire computer system, in XML. A builder program then translates this XML into source code, generating an emulator, assembler, and disassembler - all from the same originating file.
See http://em.ulat.es for a full explanation and demo.