May has arrived and so the new set of free games for Xbox 360. In May Xbox Live Gold members will get Dust: An Elysian Tail and Saints Row: The Third.
From May 1st until the 15th, Gold members can download Dust: An Elysian Tail for free — usually a $14.99 game. Then from May 16th and until the end of the month subscribers can download free Saints Row: The Third. This is a $19.99 game, but as an Xbox Live Gold members you can download it for free.
About the promotion: Some time ago Microsoft started offering 2 free Xbox 360 games each month, but it was going to last only until the release of Xbox One. And because of its success, Microsoft decided to make the offer permanent, and some time in 2014 the company is also planning to offer 2 free games but for Xbox One.
Remember that these titles will be available for a limited time only. You can do your free purchase via the Xbox 360 dashboard or via Xbox.com.
Source Major Nelson