UARS is scheduled to reenter sometime between 11 p.m. and 3 a.m. September 24. It may reenter over parts of Canada, Africa and Australia. Here's a link from NASA which provides more in-depth updates. The FAA has also issued an advisory of sorts.
UPDATE 9:56 p.m.: Observers in Texas saw UARS overhead still in orbit around 9:18 p.m. EDT. It has not yet begun to reenter.
UPDATE 10:58 p.m.: UARS will reenter over parts of Canada, Africa and Australia (as well as over the Pacific, Indian and Atlantic oceans) between 11:45 p.m. and 12:45 a.m. EDT. For more updates, check out this NASA link. Spaceflight Now has live tracking data available on its site.
UPDATE 11:39 p.m.: UARS is apparently on its last orbit.
UPDATE 11:46 p.m.: Within an hour of reentry.
UPDATE 12:54 a.m.: An unconfirmed report came through that UARS came down somewhere in Northern Quebec. No idea is this is true. Waiting on positive confirmation.
UPDATE 1:56 a.m.: I am really tired. No confirmation from NASA yet as to where UARS is now located. It is widely believed the satellite is down. I am going to bed...I will update this post tomorrow.
UPDATE 10:14 a.m.: NASA has confirmed that UARS reentered sometime early this morning. It is believed it went down over the Pacific Ocean, although no one has confirmed this yet.