If you're an Assassin's Creed fan and an Xbox Live Gold member, you'll want to keep an eye on the calendar. Assassin's Creed II will be the next game featured on Xbox Live's "Games with Gold" program.
Assassin's Creed II normally runs 1600 Microsoft points (about $20) but between July 16th and 31st, you can download it for free with your Gold Membership.
We mentioned it with the Xbox 360 Ultimate Game Sale but the current "Games with Gold" title is Defense Grid: The Awakening. Defense Grid is available as a free download through July 15th to Xbox Live Gold members.
You can find all the details on the "Games with Gold" program here at Xbox Live.
Source: Xbox Wire; Thanks, Rat, for the tip!