Sony just revealed the free games coming to PlayStation Plus subscribers for August 2014.

PlayStation 4
Road Not Taken (PS4)
Fez (PS4, PS3, PS Vita)

PlayStation 3
Crysis 3 (PS3)
Proteus (PS3, PS Vita)

PlayStation Vita
Metrico (PS Vita)
Dragon's Crown (PS Vita, PS3)

Games marked with additional platforms should be cross-buy applicable. That means if you get Fez on one platform, you get it for the other two. The same should apply to Proteus, and Dragon's Crown.

Europeans get pretty much the same list of games as above with one notable exception. Instead of Dragon's Crown on the Vita, you will get LEGO Harry Potter Years 5-7.