What happens when a temporary pilot certificate expires? What can I do if my not-so-newly issued temporary pilot certificate is about to expire and I haven't gotten my permanent certificate yet?  Is there any way that I can keep flying while waiting for it, and is there a way to check on the status of the permanent certificate?
According to this AOPA article, you can request an extension online through the FAA's Airmen On-Line Services.

You also can look up your current status here: 

http://www.faa.gov/licenses_certificates/airmen_certification/new_verification_info/

In my case, this was updated about a week before my card arrived in the mail.

You can also see what date's submissions they have processed here: 

http://www.faa.gov/licenses_certificates/airmen_certification