Twine is an open source (GPL) program that uses wiki formatting to create hypertext. Often people refer to Twine creations as "interactive fiction" or "choose your own adventure stories", but I'm just going to refer to them as games.
The Twine program is available (for free) for Windows, Mac OS X, and there is even "twee" a command-line version that uses Python. A game is organized in a nice graphical interface that shows connections between passages and points out any broken links. Once finished, the program generates a single HTML page which contains the entire game.
Finally, here are a few Twine games that I
enjoyed found noteworthy. Some of them are disturbing or offensive (because sometimes art can be disturbing or offensive). Some of them use the f-word a lot. Several popular Twine game designers are transgender and use their games as a medium to share their experiences and feelings.