40 minutes to go, and the last we've heard is that the two sides are "close" on a record deal. We should be hearing something soon. Stay tuned.
UPDATE [4:45pm]: Fifteen minutes to go and still nothing. When the Yankees traded for Randy Johnson a few years back they were granted an extension to their exclusive negotiating window, so there is definitely some precedent for it should the Mets and Santana be unable to come to terms by 5pm. The deal is in the best financial interests of baseball, so look for the commissioner's office to do whatever it can to make sure this contract gets done.
UPDATE [5:00pm]: Well, it's 5pm EST and there's no news. In this case, no news is *not* good news. I don't think it's going to fall through or anything, and I know that an extension window will be granted if necessary, but I really don't feel like sitting around in the fetal position for another 24, 48, or 72 hours while they hammer this thing out.
UPDATE [5:08pm]: According to Jon Heyman at SI.com, the Mets have requested a two-hour extension to finalize the details of their contract with Santana. If they are only asking for two hours (as opposed to two days or somewhere in between) they must be pretty close to getting this thing done. Stay positive, folks. We're almost there.
UPDATE [6:45pm]: According to Steve Popper and others, the deal is done. All that is left is for Santana to take a physical.