September is just around the corner. The Xbox One free games for the month are Prison Architect (September 1-30) and Livelock(September 16-October 15), which normally sell for $30 and $10 USD respectively. The Xbox 360 free games are Lego Star Wars III: The Clone Wars(September 1-15) and Sega Vintage Collection: Monster World (September 16-30. The Xbox 360 Games With Gold titles play on Xbox One through backwards compatibility, so Xbox One owners are actually getting four freebies.
As an added bonus, For Honor is still free all the way till September 15th. Enjoy!