FamilySearch.org has invaluable records for people researching their family history in Philadelphia. The city death certificates are the real prize because you can view the original documents. I was able to find death dates I didn't have, as well as young children who died between censuses. I even found maiden names and parents that I didn't know about.
Go to
http://pilot.familysearch.org
Select "Canada, USA, and Mexico" from the drop-down box
Scroll down to
Pennsylvania, Philadelphia City Death Certificates, 1803-1915
Pennsylvania, Philadelphia Marriage Indexes, 1885-1951