Today, Aug. 16, 2008, will be the first meeting of McCain and Obama on the same stage at Rick Warren's megachurch, Saddleback. They have not been on the same stage together since before the primary season began.
Last I knew, the issues slated to be discussed were Rick Warren's pet issues of poverty, AIDS, and the environment. That the first major political discussion is being held at a church rather than in the (secular) public arena is a concern for many, who see the "wall of separation" between church and state beginning to crumble (if it ever really held very firm to begin with). Both candidates are clearly seeking the much coveted evangelical vote.
See background from NYT here. And I posted on this a while back here.
UPDATE: See some early results of the event here.