Open Source Game Clones lists hundreds of them, from Oolite to Freeciv with many you haven't heard of in-between, categorized and ordered for your entertainment.
This site tries to gather open-source or source-available remakes of great old games in one place. If you think that something is missing from the list – please go to our GitHub repository and create an issue or even a pull request! Since all these projects are open-source you can help them and make this world a better place. Or at least you can play something to appreciate the effort people put in them.
Similar resources—consider the formal definitions of the terms—include the Open Source Game List, Awesome Open Source Games and Free Gamer.
Previously:
• Where to get free games
• I'm afraid to die in games
• The existential dread of fighting games
