Classic Traveller is an amazing scifi role playing game dating back from 1977 and still played today - a 5th version is out. Since today is FreeRPGDay, I guess Marc Miller decided to make this one free....
Very well-made detailed maps, but the costs add up quickly if you’re a regular user. I’m not a gigantic fan of paying 1-4 USD for each individual map a-la-carte rather than paying for a pack....