The Washington Post says Gore's door is ajar:
Although saying he has no plans to run for president in 2008, former vice president Al Gore has nonetheless left the door ever so slightly ajar. It's a good bet that door will swing open a good bit wider come next May. That is when Gore is scheduled to publish his next book. With no fanfare, he signed a few weeks ago with Penguin Press to write 'The Assault on Reason.' As described by editor Scott Moyers, the book is a meditation on how 'the public arena has grown more hostile to reason,' and how solving problems such as global warming is impeded by a political culture with a pervasive 'unwillingness to let facts drive decisions.'
Source: Washington Post