Sometimes it's good to be an Xbox Live Gold subscriber.
Larry "Major Nelson" Hyrb announced that Assassin's Creed II joined the Games With Gold program, meaning gamers with that level of membership can download it free-of-charge. Originally released in 2009, the game introduced players to Ezio Auditore di Firenze, who stuck around for two sequels, Brotherhood and Revelations.
If you prefer something else, a lot of Games On Demand are on sale today, running through Monday, July 22nd. These include Asura's Wrath, Mortal Kombat and Resident Evil 5 at $9.99 apiece, along with Ultimate Marvel vs. Capcom 3, Super Street Fighter 4: Arcade Edition and Devil May Cry: HD Collection for $14.99 each. These deals won't last, though, so you might want to hurry and take advantage.