The original UNIX Rogue is now available for play online, free. Rogue is the game that started the cascade of number-driven ASCII worlds over the past 30 years. Michael Toy and Glenn Wichman programmed the game in C, using the then-new curses.h library. They were university students at the time, and Rogue was distributed across university and public networks over the next 30 years as free, open-source software. The creators retain copyright despite open-sourcing their creation.
A new website has appeared: rlgallery.org, the Roguelike Gallery. Currently the site hosts 2 versions of Rogue, with plans to expand. The website hosts the scores of all the players, including online leaderboards and game replays. You can watch others in real-time as they explore the Dungeons of Doom.
Simply SSH to rlgallery.org. You probably need to use a terminal emulator, and I recommend PuTTY, a free Telnet/SSH client. The username is "rodney" and the password is "yendor".
If you have no idea what I'm talking about, Telnet and SHH are text-based internet protocols. They are Pre-Web technology, but are still very fun and easy to use.
I encourage all readers to give Rogue a try and set some high scores on rlgallery.org!