Turn-based strategy games are a genre of games including the Civilization series, Alpha Centauri and others. Turn-based strategy games typically simulate empire-building and involve complex strategy and long playing times. Multiply the boardgame Risk by chess and you have a rudimentary model for a TBS game.

These sites are a great resource and community for the Civilization series, Alpha Centari and other TBS games.

• CivFanatics Forum: I go here to learn about Civilization III strategies and read how others play the game. There is also a very strong CivII community there and I anticipate they'll be strong when Civ4 is released.
• Apolyton CS Forums: This is the best Alpha Centauri forum I've found. They also have boards for the other games, but I read CivFanatics for the other games.