Dear Pat -
Documents for the aircraft -
Registration certificate, airworthiness certificate, radio station licence, aircraft lease agreement, aircraft insurance certificate...
Documents for the flight -
ATC flight plan, overflight permits, traffic rights, landing permits (varies for scheduled or charter flights), handling agreements, airways and landing fee agreements (means for billing), fuel carnet or credit cards... charts and maps for route to be flown, and airports (departure, destination and alternate airports)... Also a computer flight plan or flight release form...
Documents for passengers or freight -
Passenger or cargo manifest, dangerous goods notification, weight & balance sheet...
Documents for crew -
Licences (sometimes passport or ICAO crewmember certificate) - crew visa if required by some countries...
I probably forgot some documents which are used by some airlines, and may be also the case that some documents listed above not always required...