The 3.19 patch for Civilization IV : Beyond the Sword is available for download from Firaxis.

There are no major changes but some interesting bug corrections and few modifications (one of them is that you don't need anymore to introduce the CD in order to start the game).

New modpacks for Civ4 Colonization are available in the Downloads section.
Access it directly from here.

The official website of Civ4 : Colonization has been revealed.
Discover it here.

The next extension of Civilization IV : Colonization is expected on September 26th in Europe (22nd in USA and Canada).

Previews of Civilization IV : Colonization have been published by Gamespot and Gamespy.
You will learn there that food is a key point for victory in the game, by developing demography of the colonies (with corp and fish).
Education of the population is also very important because it allows the appearance of specialists (carpenter, lumberjack, blacksmith, etc.) that themselves allow you to build new things and also allow you to use new resources.

The IGN website revealed some information on factions of Colonization : the Dutch, the English, the Spanish and the French.