Brent P. Newhall's Musaeum of Fantastic Software Wonders

O'Neill's Dream is a free Gundam fan RTS game where you mine asteroids to build mecha and colonies to fight off pirates and other mecha.

The Explorer's Tale is a free Android app of collaborative world-building. Each of the three players chooses their role using the Explorer's Tale app, which tells them what to say to each other. Everyone else is part of an active audience.

Blades in the Dark Score Generator creates a random "score" for the tabletop RPG Blades in the Dark.

The Plot Engine builds plots suitable for a fantasy tabletop RPG like Dungeons & Dragons.