The Philadelphia City Commissioners are the Election Board and the Voter Registration Commission rolled up into one. They are the definitive source for Philadelphia-specific election-related information.
VoterWeb is a great system for managing voter contact, printing street lists, targeting active voters, and more.
The generally accepted rules of the Democratic Party of Philadelphia were written in 1954. They are on file with the Philadelphia Board of Elections. They are available only as paper copy or a scan of a paper copy. Here is a text transcription of that scan.