byuu - Multi-system emulator focused on performance, features, and ease of use.
QEMU - Generic and open source machine & userspace emulator and virtualizer.
Quickemu - Simple script to "manage" Qemu virtual machines.
Shoebill - Macintosh II emulator that runs A/UX (and A/UX only).
PCE.js - Emulates Mac Plus, PC, & Atari ST in asm.js & WebAssembly.
Citra - Nintendo 3DS Emulator.
Dolphin - GameCube and Wii Emulator.
gdbstub - Implementation of the GDB Remote Serial Protocol in Rust, primarily for use in emulators.
PyBoy - Game Boy emulator written in Python.
SameBoy - Game Boy and Game Boy Color emulator written in C.
Kopycat - Multi-architecture hardware emulation solution.
libz80 - Emulator of the Z80 processor (C library).
Ruffle - Flash Player emulator written in Rust.
JSLinux - Run Linux or other Operating Systems in your browser.