What are all of the preferences files used by iTunes X and iTunes XI?
This answer is in two parts. If you're after all the preference files associated with iTunes then the list is relatively short. If you want every file that iTunes accesses then the list is going to be vastly and incredibly long and also very difficult to track down. If you can offer some more context of what reason you're trying to track these down maybe I can help you isolate files related to your needs.

All of iTunes preference files:

File (Primary): com.apple.iTunes.MACHINE_GUID.plist

Located at: /Users/USERNAME/Library/Preferences/ByHost

Files: com.apple.iTunesHelper.plist | com.apple.iTunes.plist | com.apple.iTunes.eq.plist

Located at: /Users/USERNAME/Library/Preferences

Hidden File: .iTunes Preferences.plist

Located at: /Users/USERNAME/Music/iTunes/iTunes Media

All of the settings you set/change in the iTunes application are represented in the two primary preference files. The one in the ByHost folder above and the other main one called com.apple.iTunes.plist above.

Hope that helps.