There are currently at least two spots open for July 2009 on the East Coast. I can't be more specific than that; otherwise, I compromise my anonymity.
From what I understand, keeping close ties with your home department's PD - meaning, also, that you've been assiduously kissing ass since you arrived on campus - is one of the best ways to be in the know about off-cycle openings, as the PDs will know where they are. They'll provide the behind-the-scenes recommendations and tips that will push an applicant forward for these rare vacancies.