Lunar Orbiter Photographic Atlas of the Moon - Digital edition of Lunar Orbiter Photographic Atlas, 1971, with all 675 plates. - http://www.lpi.usra.edu/resources/lunar_orbiter/
A History of the Lunar Orbiter Program - The NASA History Office offers a detailed history of the program startup, technical background, spacecraft manufacture, and mission summaries. - http://www.hq.nasa.gov/office/pao/History/TM-3487/top.htm
Lunar Orbiter to the Moon - Information and data on the five lunar orbiter missions (1966-1967). - http://www.solarviews.com/eng/lunarorb.htm
Wikipedia: Lunar Orbiter program - An overview of the five unmanned Lunar orbiter missions launched by the United States in 1966 through 1967. - http://en.wikipedia.org/wiki/Lunar_Orbiter_program
Lunar Orbiter Program - Overviews of the various Lunar Orbiter missions, with photographs and related links. - http://www.lpi.usra.edu/expmoon/orbiter/orbiter.html
Lunar Orbiter - Detailed information, experiments, data, and images on the five survey missions (1966-1967). - http://nssdc.gsfc.nasa.gov/planetary/lunar/lunarorb.html