Altair32
   An open source Altair emulator for Windows.
   http://highgate.comm.sfu.ca/~rcini/classiccmp/Altair32.htm

CP/M
   An open source CP/M-80 ver2.2 emulator for MacOS.
   http://homepage3.nifty.com/bugbug/cpm/

Chip-8 Emulator
   A freeware Chip-8 emulator for DOS.
   http://members.aol.com/autismuk/chip8/

Desktop Cyber
   An open source CDC (Control Data Corporation) Cyber 6x00, 7x or 17x type mainframe emulator for Windows or Unix.
   http://members.iinet.net.au/~tom-hunter/

Emu28
   An open source HP18C/28C emulator for Windows.
   http://privat.swol.de/ChristophGiesselink/emu28.htm

Emu51
   An open source 8051 emulator for Linux and Windows.
   http://emu51.sourceforge.net/

Emula3
   Contains emulators for many different computers and calculators/PDAs for many different platforms. [English/Italian]
   http://www.emula3.com

Emuviews
   Great emulation page maintained by JoseQ, maker of the famous Rumor Mill, many downloads, great layout - some hosted sites.
   http://www.emuviews.com/

Evenson Consulting Services' SWTPc 6800/6809 Emulator
   Windows 9x/NT GUI emulation of SWTPc 6800 and 6809 systems. A Simulated Machine Environment (SME) emulation plus .dsk file downloads.
   http://www.evenson-consulting.com/

Flexemu
   An open source EurocomII/V7 emulator for Linux and Windows.
   http://geocities.com/flexemu/

FunnyMu
   A freeware Creativision, Funvision, and Whizzard emulator for Linux/SDL.
   http://www.lemoncube.com/26.html

HiRISC Simulator
   A freeware emulator for Windows of a system designed specifically for the Applied Systems Programming course at the University of Akron.
   http://www.cs.uakron.edu/~margush/307/HiRISC/

James the Animal Tamer's Emulators
   Freeware APF, Aquarius, Exidy Sorcerer, Interact Family Computer, MC-10, NEC PC-6001A, Panasonic Personal Computer, and TRS-80 emulators for Windows.
   http://www.geocities.com/emucompboy/

Japanese Computer Emulation Centre
   A site dedicated to the emulation of Japanese Machines including X68000, PC6001, PC88, PC98, MSX 1/2/R, Sharp MZ, Sharp X1, Fujitsu FM7, and Fujitsu FM Towns.
   http://www.jcec.co.uk/

KCemu
   An open source emulator of the KC85 homecomputer series for Linux and Windows.
   http://kcemu.sourceforge.net/

Project8080
   Covers the development of a Heathkit H8 emulator on Macintosh.
   http://members.aol.com/heath8080a/

SIMH
   An open source collection of emulators for Windows of historical computers, including GRI-909, HP 2116/2100/21MX, IBM 1401/1620/1130/System 3, PDP-1/4/7-11/15/VAX. Also provides software kits, system photographs, and technical papers.
   http://simh.trailing-edge.com/

SPRINT
   A freeware Sprinter emulator for Linux/i386 and Windows.
   http://shaos.ru/nedopc/sprinter/sprint.htm

Solace
   An open source Sol-20 emulator for Windows.
   http://www.thebattles.net/sol20/solace/solace.html

Virtutech Simics
   A commercial Alpha, PowerPC, SPARC, x86 and x86-64 emulator.
   http://www.simics.com/

cinc
   An open source Bell Labs cardiac emulator for Linux and Windows/Cygwin.
   http://sourceforge.net/projects/cinc/

mic1
   A Java-based simulator which implements the Mic-1 microarchitecture described in Chapter 4 of Andrew S. Tanenbaum, Structured Computer Organization, Fourth Edition. [Open source, GPL]
   http://www.ontko.com/mic1/

st20emu
   A freeware ST20 emulator for DOS.
   http://sourceforge.net/projects/st20emu/

vmips
   An open source MIPS R3000 emulator for Unix.
   http://www.dgate.org/vmips/