Free Adventure Games

I'm going to include free games that are worth playing in this section.

Previously Commercial Games:
Sam & Max Season One: Episode 4 is free for PC. Max runs for president in an emergency election.
Beneath a Steel Sky is free from ScummVM. Escape the city, uncover a conspiracy, and learn about your past.
Flight of the Amazon Queen is free from ScummVM. A pilot crashes in the Amazon jungle, revealing a sinister plot.
Mr. Smoozles Goes Nutso was updated and made free. Hypnotized Mr. Smoozles is helping aliens erase the universe.
Teen Agent is free from GOG.com. A teenager is hired as a spy to discover how a millionaire is acquiring his riches.

Free games with original stories:
A recent college graduate becomes a paranormal investigator and is called to investigate cases around the world.
Help the crooked cop Dangeresque manufacture evidence to "solve" a crime so the chief will let him go home.
Search for the legendary magical Peas of Kejick, in order to receive a reward from the King!
You play as Tim Schafer! It's a Double Fine adventure game! It has injokes! How could I possibly not add this here?
Confront the dragon "Trogdor the Burninator" for destroying your thatched roof cottage.

Fan games with original stories:
MindFactory presents a fan game that takes place between the 2nd and 3rd Broken Sword and was approved by Revolution Software.

Fan remakes:
AGD Interactive's King's Quest I remake has an improved interface, voices, improved graphics, and music.
AGD Interactive's King's Quest II remake has mouse control, voices, improved graphics and music, and new puzzles and additional dialog.
AGD Interactive's King's Quest III remake has mouse control, voices, improved graphics and music, and new puzzles and additional dialog.
The Infamous Adventures King's Quest III remake has mouse control, voices, improved graphics, music, and sound effects.
The Lucasfan Games remake of Maniac Mansion has music, improved graphics and a slimmed interface with inventory icons.
AGD Interactive's Quest for Glory II remake has improved an improved interface, graphics, and music.
The Infamous Adventures remake of Space Quest II has mouse control, voices, improved graphics, music, and sound effects.