Glorantha is the primary setting for the RuneQuest roleplaying game. It is introduced in the main rule book, which provides everything you need to generate Gloranthan adventurers from the Dragon Pass region.
The Glorantha web site provides an excellent introduction to the world of Glorantha.
Chaosium web site offers a range of guides, maps and reference material to support running and playing games in this amazing setting on their web store.
The Glorantha Wiki also has extensive reference articles on the world of Glorantha.