In North America, this week's PlayStation Plus freebie is Terraria for PS Vita.
That'll be up on the PlayStation Store as of tomorrow's update. The handheld port is similar to the other console releases but it has expanded (optional) touch functionality. And like pretty much everything else on the system, Terraria is going to look nice on that OLED screen.
Seems like a nice pick-up if you held off on this version due to its lack of Cross-Buy support. For Europe's June PS Plus lineup, head over here.
PlayStation Plus: Terraria Free for Members [PlayStation Blog]