Recommended emulators

All links here will take you to the latest build of that emulator, if you what more info regarding the emulators, either check the Emulators page.

>THERE ARE NO FUNCTIONAL 3DS, VITA, (PS3 RETAIL GAMES), XBOX 360, OR WII U EMULATORS

Multi-System

Retroarch

DOS

DOSBox

NES/Famicon

General: Nestopia

Accuracy: puNES or Nintedulator

Gameboy/Color

Gambatte

SNES/Super Famicon

General: Snes9x

Accuracy: Higan (formerly bsnes)

Master System/Genesis

General: Kega Fusion

Accuracy: Genesis Plus GX

PC Engine/Turbografx-16

General: Mednafen

Accuracy: Mednafen

Playstation

General: PCSX-Reloaded

Accuracy: Xebra or Mednafen

Sega Saturn

SSF

Nintendo 64

General: Mupen64Plus

Accuracy: CEN64 (Note, it's early in development and won't be useful for quite some time)

GameBoy Advance

General: VisualBoy Advance-M

DreamCast

nullDC

GameCube/Wii

Dolphin

Playstation 2

PCSX2

NDS

DeSmuMe

PSP

General: jPCSP

Up-and-coming: PPSSPP  

For most audio, you'll need some method of decoding ATRAC3+. FFMPEG plans to cover that, but for now you need at3tool.