Star Trek: The Dice Game is a solo, print and play game in which you manages the crew of the Enterprise through various mission challenges.
Invisible City Games offers a free board game called Aliens vs Cows. The aliens try to abduct cows. The cows try to protect the planet from the invasion.
Saucer Escape is a solo roll-and-write game about a fight against aliens in their mothership.
Dune The Dice Game is a free print-and-play game set in the world of Frank Herbert’s Dune Universe. It is inspired by the old Avalon Hill game.
Anaxis is a free space wargame, played on a hex grid with ship counters.