If you don't have this bookmarked already, this site contains important medieval primary sources, and the link below is to its Empire & Papacy primary sources: Internet History Sourcebooks
It is later than your centuries specified, but this short, concise survey of the period itself (probably required course reading still, iirc) will have a valuable bibliography:
Read the reader reviews section of this book ^ on the Amazon link for a few other topic ideas. Invocation of the Donation of Constantine to attempt to bolster papal primacy, Roman resistance to Byzantine caesaropapism, the violence during the 10th century and the beginnings of the papal schism in 1054. Also the example of powerful abbeys like Cluny in Burgundy, and the creation of the College of Cardinals in 1059 are interesting outcomes of the medieval conflict between church and state.
A very interesting process that I have also been reading about lately, though I am not very knowledgable about it. Maybe Dreamweaver, or Kirilax will have a few ideas?