The BBC Lives! - for enthusiasts of Acorn's range of 8-bit micros from the eighties: the BBC models, Electron, Master and Compact, and to a small degree the Atom and Archimedes
Bochs - x86 PC emulator written in C++, and runs on most popular platforms
Browserola - Browser emulator for Windows 95/98/NT, no longer being sold (as of January 1, 2001), though version 1.01 can still be downloaded
Computer History Simulation Project - loose Internet-based collective of people interested in restoring historically significant computer hardware and software systems by simulation
Deja Vu - emulate several old browsers, allowing the user to enter a URL and then view the page as it would have been viewed through that browser
ENIAC-on-a-Chip - project to recreate the original ENIAC, following its architecture and basic circuit building blocks as much as possible, also described in an article by Jan Van Der Spiegel
Ersatz-11 - D Bit - software PDP-11 emulator for MS-DOS and Linux PCs
Multi Emulator Super System (MESS) - sequel to MAME, except that rather that emulating arcade games, it emulates various consoles and computers
Multiple Arcade Machine Emulator (MAME) - when used in conjunction with a game's data files (ROMs), MAME will more or less faithfully reproduce that game on a PC, can currently emulate more than 1500 classic arcade video games from the '70s and '80s
Palm OS Emulator - emulates the hardware of the various models of Palm OS platform devices, intended for writing, testing and debugging applications, runs on Windows, Mac OS and Unix
Plex86 - project to create an extensible open source PC virtualization software program which will allow PC and workstation users to run multiple operating systems concurrently on the same machine
Trans Gaming - working to bring games to Linux by improving the Wine project, creating a full implementation (WineX) of the Microsoft DirectX multimedia APIs on Linux