SpaceWar running on a restored PDP-1 is demoed on the 1st and 3rd Saturdays at 2:30 and 3:15 at the Computer History Museum in Mountain View, CA.
While you are there, you also see the demos of the restored IBM 1401 (punched card computing from the early 1960's) at 11:00 on Saturdays, and Wednesdays at 3:00.
I cannot recommend this highly enough. It's a real slice of history. If you're lucky they'll actually let you play the game - which is still a fun challenge.
When I went there a few years ago, the PDP-1 demos were actually done by the original guys who programmed Spacewar! I don't know if they're still doing that, but it's magical to be in the presence of these pioneers. This industry is young enough that many of the original masters are still alive and eager to share their stories and achievements.
While you are there, you also see the demos of the restored IBM 1401 (punched card computing from the early 1960's) at 11:00 on Saturdays, and Wednesdays at 3:00.