NASA
Nasa: Shuttle Reference
This site from NASA goes into great detail about the physical makeup of the Space Shuttle, and includes sidebars with further information about NASA and the manned space program.
Shmoop University
Shmoop: Sula
The second of Toni Morrison's novels, Sula tells the story of the friendship between two African-American women. This site looks in detail at this friendship as it examines plot, character and themes found in the novel.