Help find me a game! (in Off-topic)

I'm looking for a game for coworkers and I to play.

Requirements:

* Free, or nearly so.
* Turn based, so we can submit turns at our own pace
* Windows based client (at least, optionally Mac OS X also for our artsy UI guy)
* Either one of us has to be able to host it (on a Windows box), or the hosting service must support:
- Our own games, so only a limited known set of people can join
- Our own turn schedule, or on-demand turn processing
* Some modicum of strategy and tactics.
* Games must have some "end" condition; there has to be a winner.
* Good reporting of progress from turn to turn.

Other non-requirements.

* Genre is not important, but Space Conquest, Land Conquest, etc. would probably be preferred. Time setting; modern, medieval, "old west", etc. are all fine.
* A graphical client is not necessary, but nice

Any pointers welcome. I've done VGA planets way back when (I even was one of the original PHost developers), but I think that's a bit much for our needs right now. But something LIKE that.

Civilization 3: Play The world? Its not free though.

I recommend Alpha Centauri. It's from the same creater as Civilization, but is a little older (late 90's, early 00's) and as such is much much cheaper. It has multiplayers support, and awesome replay value.

the story goes that after Civilization 2, the Earth reached an all time low and man kind chose to send a spaceship to the closest habitable planet, Alpha Centauri. On the way there, the spaceship had a critical mechanical failure. In trying to decide how to handle the situation, the ship splits into 7 distinct factions.

Tree hugging hippy Gains.
Power broker money hungry Morganites.
Eastern Philosophy and killer of the unimportant single person Hive.
The vaguely hippyish research dominating University.
God Fearing and Bible thumping Believers.
The UN pushing peace loving Peace Keepers
And the war mongering and survival guide writing Spartans.

When the ship reaches the planets atmosphere, it's 7 factions each take a different escape pod. Once landed, the goals are simple: Survival, creation, conquest.

With roughly off the top of my head 6 ways to win (research, conquest, diplomacy, cornering the energy market... and a couple more) and very customisable rules, this game will have you hooked for years. At least it has me.

Check this game out! http://redlite.org