The Annual Election Period Ends December 7th

This is according to the calendar as defined by the CMS, Center for Medicare and Medicaid Services.  You can change your stand-alone Prescription Drug Plan (PDP) or Medicare Advantage (MA) plan without restriction during this time.
Hurricane Sandy Has Affected Many
In order to help those affected by Hurricane Sandy, it appears that there is another Special Election Period.  You need to call Medicare (1-800-MEDICARE) in order to receive this extension.  It makes sense, since many have lost so much, including paperwork and personal belongings.  Presumably, this extension will also apply to those that have been indirectly affected as well, but you will need to contact Medicare yourself.
Further information can be found on the official website: