Hoplites is a free computer card game based on the excellent GMT board game SPQR. I’ve played it and its a lot of fun. The card layout is reminiscent of the play in Columbia Games’ Gettysburg and Eagles games. There are also Samurai and Conan expansions. It’s an excellent diversion when you can’t get out your miniatures. Download the game here.
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.
Magma is an abstract territory control print-and-play game from Invisible City
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.