Paid games that are free right now. Keep permanently ones are at 100% off: add one to your Steam library before the date shown and it's yours for good. Free weekends let you play the full game until the date shown; you keep your progress, and the game is often on sale.
No free weekends right now. New ones show up here as soon as Steam sets them up.
Times are in UTC. We check prices and Steam's package data around the clock, and take a game off this page as soon as its free time ends.