World building means the process to create a fictional environment for a novel, movie or in our case a game. Here I will collect some good links for you, those points on this task.
World concept Wikipedia: A good overview over world building in general. It covers the two creation methods and gives a quick overview over some construction steps. And it provides some good links to more stuff.
http://en.wikipedia.org/wiki/WorldbuildingWorld Design @ metamythos: A guide with many details what you should or could think about during your creation process.
http://www.metamythos.net/wiki/World_Design/Methods_of_CreationMapmakingAutoREALM: An open source tool to create maps. With this tool you can create concept maps if you are not skilled in painting freehand. To plan your world and visualize it for your team.
http://sourceforge.net/projects/autorealm/AutoREALM Tutorials: Here you find some basic tutorials for the tool
http://www.interface1.net/autorealm/Campaign- Cartographer: A commercial software for mapmaking.
http://www.profantasy.com/