Skylab: A Chronology. (SP-4011) by Roland W. Newkirk and Ivan D. Ertel, with Courtney G. Brooks. This book is available on-line thanks to the kind efforts of Chris Gamble.
Orders of Magnitude: A History of the NACA and NASA, 1915-1990 (SP-4406). By Roger E. Bilstein. Paperback. This book has been newly placed into hypertext format and is available for reading or downloading. Orders of Magnitude is one of the classic texts in the NASA History Series. It is a general introduction to NASA and aerospace exploration.
X-15 Research Results With a Selected Bibliography (SP-60). This short book by Wendell H. Stillwell is a useful guide to the historic, but often underappreciated, X-15 program. While the book was written approximately half-way through the program and is not a part of the formal NASA History Series, it still contains a significant amount of data and a number of clear charts and photos.
KSC Visitor Complex -- Apollo/Saturn V Center -- Opened on December 5, 1996, this is the best-preserved example of the three remaining Saturn V launch vehicles. A fitting tribute to mankind's greatest adventure. Click here to view detail photographs of the Saturn V on display there.
Ninfinger Productions -- Sven Knudson's great resource for modelers of spacecraft both plastic and flying models.
collectSpace -- Good info on news and collecting space artifacts
Project Apollo Archives -- Kipp Teague's excellent source for multipmedia related to the Apollo Program
Karl D's On-line Space Museum -- Karl Dodenhoff provides information on Apollo, EMU, and Russia's Lunar Landing Program.
Space in Miniature -- Mikes Mackowski's reference guide to modeling all types of spacecraft.
The Apollo-Saturn Reference Page -- John Duncan's site primarily about the new Apollo/Saturn V Facility at KSC. Also included: the Apollo/Saturn News Reference.