There are currently 9 free PS4 games available to add to your PSN account. Only available from March 25 8pm PDT to April 22 8pm PDT. No playstation plus required. Just log into PSN and add to your library:
https://store.playstation.com/en-us/category/9779f12f-50c8-4c07-8d20-47e21293b6c6
Ratchet & Clank is also still available for free until March 31 08:00PM PDT. Same as above, login to PSN and add to your library:
https://www.playstation.com/en-us/games/ratchet-and-clank/
Horizon Zero Dawn complete edition will be free from April 19 until May 14:
https://www.playstation.com/en-us/play-at-home/
 

https://store.playstation.com/#!/en-us/days-of-play/cid=STORE-MSF77008-DAYSOFPLAY17LP
Uncharted 4 is $20. I just bought it. I might have to put Mass Effect on the back burner.

The new PlayStation 4 firmware update will include external HHD support for game installation. Finally. I honestly didn't realize the original PS4s even had USB 3. They are also finally adding custom wallpapers via screenshots. About damn time. The wallpapers in the online store are complete garbage. I'd still prefer to use my own .jpg files like on the PS3, but modders used that feature as a way to hack the system which is why we never got the functionality in PS4. Using a screenshot is completely fine with me.
http://blog.us.playstation.com/2017/02/03/ps4-system-software-update-4-50-features-detailed/