If you're looking to plug a few hours this weekend but don't fancy splashing out on something new, then you're in luck, with two games going for free on Steam right now that you can download and keep forever.
The first is Guns of Icarus Alliance, the expanded version of steampunk airship combat game Guns of Icarus Online. The original was purely PvP, but Alliance adds PvE elements, six factions to choose from, and an ever-changing world "that is constantly being shaped and reshaped by the players".
Basically, you and some friends get control of a giant airship, and each of you will have to stick to your role—pilot, gunner or engineer—if you want to survive. It's well-regarded, and I've been wanting to play for a while. Now is the perfect time. The game is free over Memorial Day weekend "in honor of everyone who served and sacrificed" and the giveaway, which ends on Tuesday afternoon, is accompanied by an update that adds a new PvP ship and a PvE map. Grab it here.
Your second free game is Galactic Civilizations 2: Ultimate Edition, which is the regular version of the 4X space strategy game plus the Dark Avatar and Twilight of the Arnor expansions. Again, it's another solid game, and it's aged well since its release in 2011, largely thanks to a huge patch it got at the end of 2015. If you've enjoyed other GalCiv games, then at least grab it and stick it in your library to play later.
It's not clear when the GalCiv 2 giveaway ends: Steam says it's free "until Saturday 5/27 at 10 Pacific"—but of course, today (Saturday) is the 26th rather than the 27th. And whether it's 10am or 10pm is anyone's guess. Basically, if you want it, pick it up now.