Maybe you want to check out cosmic supremacy? It has some interesting features. Its a space strategy game. Its free (at least it says so). It has a lot of borrowed things from Civ (as far as I can see). And the interesting thing is that it is massively multiplayer (at least it says so). That combination with a turn based strategy game of game depth a la civilization is actually new to me.
Hi.. I'm one of the players who have tried Cosmic Supremacy, and I'm still a rather active member of their community (well, the game has been around 5 years or so now - I think - but I've only played it for a year, and hooked for a year) ..
Though I was wondering why Cosmic Supremacy seldom gets more attention (I think it does deserve it) - maybe it suffers the same situation like what Njordin mentioned with Star Ruler (first time I've been directed to that site myself) - it's developed mainly by one guy, and the marketing skills is also ermm.. questionable.. The game used to be called Space Civilisations, but I think due to it sounding like GalCiv (or some other thing that I wasn't aware about that happened before I knew of the game), it was renamed Cosmic Supremacy.
Anyway, I only skimmed through this forum thread, and noticed Cosmic Supremacy was mentioned at least twice though, but no one seemed to follow up on it.. I can testify that the game is free and ad-free (starting last year, the way the game is financed changed in that only a few players make an annual donation to keep it free - I'm one of the players who chip in, willingly too, and we only need to cover server costs anyway - the developer himself doesn't earn from the game.
About claims of massive multiplayer, while it's not 1000s of players in a game, but it is true that each game typically has at least 10-20 active players, sometimes even 30 or more players - some players sit out certain games, but every game I've played, I've met nearly different people with different playing styles (although some are familiar faces too), which I think makes the game that much more replayable.
It does draw inspiration from MOO and Civ (never played Civ myself before actually), but I find it is a totally different experience compared to other games. It's still a turn-based game, but requires the player to really make strategic moves and efficient use of his/her resources. There's a 3D map that makes things a bit more interesting for me personally, because you then have to decide whether to send your fleet against your neighbours, or whether you should just make peace with them, or even join forces with them. There's no AI, but like I mentioned earlier, you go up against real players that have varying styles of play. It's a bit like chess - finite number of possible moves, but no one game ever really the same.
I also like the fact that the game allows you to actually use simple programming kind of scripts to run your 'empire', so you don't have to do the micromanagement all the time, but you dont gain a direct advantage just by using these scripts over your opponents, nor can you buy with real cash for an advantage in-game.
There are a few drawbacks maybe, in that it does take a lot of time, and quite a bit of skill from a player to play a competitive game. Learning the game might be a daunting task, but it's not really that complex - actually I think it's slightly too simple in some aspects. There's also a need to download the client to play the game (it's only 7+MB anyway if I remember correctly), and there's really nothing dodgy about it - that was my first impression when I tried that game, but I've never regretted downloading it.
So ermm.. I think I got carried away writing about this, but I just wanted to do my part in spreading the word about the game.
p.s. I also just downloaded FreeOrion, and planning to give it a shot too..