The Xbox One will see two titles available, Crimson Dragon and Strike Suit Zero: Director's Cut. Unlike their 360 counterparts, both of these games will be available for the entire month, though it's likely better to download them early so you don't forget.
On the 360 side of things, gamers can grab XBLA offering, Motocross Madness, from August 1st through August 15th. For the remainder of the month, Dishonored will be freely available to Gold Members. Keep in mind, however, that both of these games do have DLC with achievements, so they cannot be completed simply by downloading the core title.
Sourced Via True Achievements