Ariane 5 Accident Report (html)
Mars Climate Orbiter Press Release (html)
Mars Climate Orbiter Report (pdf)
Mars Climate Orbiter Charts (pdf)
An Analysis by James Oberg of IEEE Spectrum (htm)
Mars Polar Lander External Report Part 1 (pdf)
Mars Polar Lander External Report Part 2 (pdf)
Mars Polar Lander External Report Summary (pdf)
Mars Polar Lander JPL Report Part 1 (pdf)
Mars Polar Lander JPL Report Part 2 (pdf)
Mars Polar Lander JPL Report Part 3 (pdf)
Mars Polar Lander JPL Report Part 4 (pdf)
Mars Polar Lander JPL Report Part 5 (pdf)
The full Roger's Commission Report on the Challenger Accident (html) Report is now on the web. Be sure and read the wonderful and often-cited Feynman appendix (Personal Observations on Reliability of Shuttle).
The report is well worth reading, but there is also an abstracted version of Challenger Report (html) available that includes the Feynman appendix.
Titan IV B-32/Centaur/Milstar Report (.doc)
Warsaw Report (html)
American Airlines Cali Accident Report (html)
Nagoya Report Table of Contents (html)
Nagoya Report Part 1 (html)
Nagoya Report Part 2 (html)
Nagoya Report Part 3 (html)
Nagoya Report Part 4-7 (html)