Here's a blurb from the FreeCol website:
FreeCol is a turn-based strategy game based on the old game Colonization, and similar to Civilization. The objective of the game is to create an independent nation.So it's a little like FreeCiv. FreeCol somehow escaped my attention, but I tried it out a little bit and it looks great. In addition to single player, you can also join multiplayer games over the internet. I'm not sure about the security implications of that, since Java 1.5 is outdated. From what I understand, only the web browser plug-in was vulnerable, but maybe someone can weigh in with a comment. I only do single player, anyway. It's humiliating enough when the A.I. kicks my ass ;)
You start with only a few colonists defying the stormy seas in their search for new land. Will you guide them on the Colonization of a New World?