The Wolfram Machine project is an effort to create a set of documentation and useful modules (both hardware and software) for a computing architecture based on the mathematical theories presented in Steven Wolfram's book _A_New_Kind_of_Science_.
CabFE is a multi-emulator frontend for MAME, Daphne and other arcade games designed specifically for arcade cabinets using minimal set of controls (typically only a joystick and a few buttons) that are common on cabinets.
This is an attempt to make a complete, and playable atari emulator entirely in python and some common modules. Currently, it only requires PyGame 1.5.0 and Numeric.
The Free 6502 emulator is a portable, extensible and configurable library for emulating the 6502 processor, used in many older computers and video games. It is aimed at reliability and speed, to allow it to be used to emulate any system based on the 6502.
The GNUton project is a re-implementation of the (defunct) Apple Newton platform.
It consists of the virtual machine, storage architecture and templates for GUI and general OS features. It aims to support execution of existing pure NewtonScript packages