This entry links to a USCIS communication to help improve customer service. The link is actually to ILW.com because the communication is easier to find there than on USCIS.gov.
At any rate you can see the steps that are required to make an inquiry on your case -- if it has gone beyond normal processing times.
http://www.ilw.com/immigdaily/news/2009,0812-casestatus.pdf