Imperialism II is free, I played it a bit and it was a pretty fun game. Unfortunately it is also extremely fast paced with the colonizable land being gobbled up in a handful of turns :/
Imperialism II, never lived up to the original. Though it added some further unique concepts such as spies and as stated earlier the New World, however the span of technology made keeping an Army and an Empire(with the consideration of the pace, at which the game was played) made it far too unmanageable.