A PC hardware informaion and review website, operated by Dr. Thomas Pabst, a German doctor.
Dr. Pabst is known to take a critical view of Intel. He has often been accused of having an anti-Intel and a pro-AMD bias. However, in August, 2000 he exposed major flaws in the Pentium III 1.13 GHz CPU, leading to Intel's recall of the product. This gained Tom much noteriety and vindication.
Despite its recent 15 minutes of fame, Tom's Hardware Guide has been around for many years, at least since 1996, when its URL was sysdoc.pair.com
See also Anandtech.