Martin regularly updates his own website with news of his other, non-Ice and Fire books and writes frequently on his blog about his life and interests.  News about his most popular series, however, has been few and far between.  The "Ice and Fire Update" page was updated in February, 2007 and then again, most recently, in January 2008.  Both of these updates by Martin seemed to say approximately the same thing: that he was working on it, that there had been problems, that it was not finished yet but when it was the fans would know as soon as possible.  Wikipedia has a useful summary of the problems with A Feast for Crows, explaining that the delay in publication was due to

a series of problems that arose during the writing of the novel. George R. R. Martin originally planned for the fourth book to be called A Dance with Dragons with the story picking up five years after the events of A Storm of Swords (primarily to advance the ages of the younger characters). However, during the writing process it was discovered that this was leading to an overreliance on flashbacks to fill in the gap. After twelve months or so of working on the book, Martin decided to abandon much of what had previously been written and start again, this time picking up immediately after the end of A Storm of Swords. He announced this decision, along with the new title A Feast for Crows, at the World Science Fiction Convention in Philadelphia on 1 September 2001 [1]. He also announced that A Dance with Dragons would now be the fifth book in the sequence.

Martin has also explained publicly that much of the material that he intended to make part of Crows will now be part of Dragons, albeit in a much-rewritten form.  The increasing length of the fourth book spurred Martin to divide it in half.  Wikipedia goes on:

[W]hen the novel was nearing completion his publishers realized it was significantly longer than A Storm of Swords and requested it be split in half for publication. After initially considering publishing it as 'Part 1' and 'Part 2', Martin's friend and fellow author Daniel Abraham suggested splitting it by POV and location instead, which Martin agreed with. Thus A Feast for Crows only contains the POV characters from the South of the Seven Kingdoms and the Iron Islands. The characters in the North, in the Free Cities and in Meereen (including fan-favourites Tyrion Lannister, Jon Snow and Daenerys Targaryen) will return in the fifth book. The split of the novel also meant that the series would be seven rather than six books long. A Dance with Dragons remains the title of the fifth book.

Amazon.com lists September 30, 2008 as the expected release date for Dragons, but Amazon dates for as-yet unpublished books change frequently and should be considered unreliable at best.  The September date is consistent with Martin's current estimated time of completion of late 2008. 

The fact that Martin is still writing obviously means that no final manuscript has been sent to his publisher for printing.  Martin's publisher, the Bantam Dell Publishing Group's Spectra label, has no current news on when fans can expect the newest book.  Given that final editing and publication takes at least a few months when rushed (as books as anticipated as this often are), Martin has only a matter of months to submit a manuscript to Bantam if he wants Dragons published any time this year.