morsecode.me
Perhaps the only of its kind, morsecode.me is a live, online Morse code radio; the most arcane of chat rooms. Users can communicate with one another only by keying Morse. Fortunately the site also comes with a cheat sheet and live translation.
I built morsecode.me after I learned Morse and later realized I had nobody to geek out with. The morsecode.me community continues to thrive, and I still actively maintain the project.