Opus Dei literally means "Work of God." Many of its members call it simply "the Work." It was founded by the Monsignor
Josemaria Escriva (now a saint) on October 2, 1928, in
Madrid. Escriva was a
charismatic fellow who taught a rather
conservative back-to-basics kind of
theology, which atracted a large number of followers. Upon his death in 1975, the Opus Dei had thousands of followers, and had spread far beyond
Spain.
The mission of the Opus Dei is for every person to seek holiness in their daily work. All men are called to be holy, the Bible says. Escriva taught that to be holy, one does not need to cloister oneself in a monastery. If your work is done for the glory of God, you can sanctify everyday work.
The present Prelate of Opus Dei is Bishop Javier Echevarria. Opus Dei has a website at http://www.opusdei.org
A little note here, I am not a memeber of the Opus Dei. In fact I disagree with many of their practices. However, I have become friends with many people who are members of Opus Dei, and I respect them and what they're trying to achieve.
As for the conspiracy theories, I cannot say for sure if they're true or not. But that's the way it is with conspiracy theories, isn't it?