I've been throwing together some web-playable retro arcade games:

Rally-X: https://linsomniac.github.io/rally-xy/

Tempest: https://linsomniac.github.io/teapot/

Dig-Dug: https://linsomniac.github.io/digger/

And not an arcade game, but a multi-player throwback to a multiplayer shooter game my team used to play called nSnipes: https://github.com/linsomniac/isnipes

iSnipes does require downloading and running a server, the others you just play on the web.