Emulation Software

Amiga

 * UAE (open source, Amiga, website)
 * VICE (open source, Amiga, website)

Amstrad CPC

 * Arnimedes (freeware, CPC, website)
 * Arnold (open source, CPC/CPC+/KC compact, website)
 * CPC++ (shareware, CPC, website)
 * CPCE (freeware, CPC, website)
 * CPCEmu (open source, CPC, website)
 * WinAPE (freeware, CPC, website)

Arcade

 * MAME (open source, Arcade, website)
 * MESS (open source, Arcade, website)
 * Retrocopy (freeware, Arcade, website)

Atari

 * Atari800 (open source, Atari 800/800XL/130XE/5200, website)
 * EMU7800 (open source, Atari 2600/7800, website)
 * Hatari (open source, Atari ST/STE/TT, website)
 * Javatari (open source, Atari 2600, website)
 * ProSystem Emulator (open source, Atari 7800, website)
 * Stella (donationware, Atari 2600, website)

C64

 * CCS64 (shareware, C64, website)
 * Frodo (open source, C64, website)

Macintosh

 * Basilisk II (open source, 68000, website)
 * KEGS (open source, Apple IIgs, website)
 * OpenEmulator (open source, Apple II, website)
 * Mini vMac (open source, Macintosh, website)
 * PearPC (open source, PowerPC, website)
 * SheepShaver (open source, MacOS, website)
 * vMac (open source, Macintosh, website)

Nintendo

 * bsnes (open source, NES/GB/GBC/GBA/NDS, website)

Sega

 * Gens32 (freeware, Genesis/Mega-Drive/Sega-CD/Mega-CD/32X, website)

x86

 * Dioscuri (open source, X86, website)
 * DOSBox (open source, X86, website)
 * DOSEMU (open source, DOS, website)
 * JPC (open source, X86, website)

ZX Spectrum

 * Fuse (open source, ZX Spectrum, website)

Other

 * Daphne (open source, LaserDisc, website)
 * GXemul (open source, generic, website)
 * Hercules (open source, System/370, ESRA/390, z/ARCH, website)
 * QEMU (open source, generic, website)
 * KEEP - Keeping Emulation Environments Portable (open source, generic, website)
 * TOTEM - Trustworthy Online Technical Environment Metadata Database