Here are a few additional NASA imagery Web sites that you may find helpful:

JSC Digital Image Collection - http://images.jsc.nasa.gov
9,000+ press release photos from all NASA manned space flight programs, including Shuttle missions up to STS-79. Low resolution imagery only. No longer updated.

Gateway to Astronaut Photography of Earth- http://eol.jsc.nasa.gov/sseop
The entire collection of catalog records for the more than 400,000 photos of Earth taken during manned spaceflight missions, most with low resolution imagery. Some high resolution images. Continuously updated.

NASA Image eXchange (NIX) - http://nix.nasa.gov
A search tool which can search imagery databases throughout NASA, tying together over 442,000 images.

NASA Human Space Flight Web, Multimedia Gallery - http://spaceflight.nasa.gov/gallery
Press release photos from shuttle missions since STS-82, press release photos from the space station, and video, audio, and animation files from the shuttle and space station programs. Also contains some pre-shuttle multimedia. All new press release photos and other multimedia are published here. Low and high resolution imagery. Continuously updated.

KSC Shuttle Photo and Video Archive - http://science.ksc.nasa.gov/shuttle/photos
Preflight, launch, and landing photos and videos from shuttle missions since STS-67. Low and high resolution images available. Continuously updated.

GReat Images in NASA (GRiN) - http://grin.hq.nasa.gov
Over 1000 NASA images of historical interest. Images available in low, high, and very high resolutions - suitable for publishers and the media. Frequently updated.