JSEmu
A collection of emulators written in JavaScript, including a Sega Mega Drive/Genesis emulator. It's a great example of a web-based emulator project.
Visit ProjectEmularity
A project focused on making web-based emulation simple and accessible, often using WebAssembly for better performance.
Visit GitHubEmuJs
A web-based emulator hub that provides a platform to play many different retro consoles, including Sega systems.
Visit Website