I'm not sure what the folks at GOG are smoking this week but they are
giving away copies of
Ultima IV right now. Seriously, they are giving away one of the seminal RPG's of the genre away for free. Sure the game is a bit dated but you're looking at one of the most influential RPG's of all time and it is being given away for free.
Populus has also made it's way
to the service although it will set you back $5.99. It's one of the foundational games of the "God Game" genre so $6 to play so that's a pretty damn good deal.
As always both games are DRM free and will run on any modern computer so go nuts.