Essentials of the Upanishads 
Detailed essay on the Upanishads, with quotes and background information. Includes downloadable e-book of the Isa Upanishad.
http://www.dvaita.org/shaastra/upanishad.htmlThe Upanishads: Max Mueller
Complete text of Muellers' two volume Sacred Books of the East translation of the Upanishads.
http://www.sacred-texts.com/hin/upan/index.htm
An Introduction to the Upanishads
Translations of eleven of the principal Upanishads.
http://sanatan.intnet.mu/
Kena Upanishad
An English translation of the Kena Upanishad (also known as the Talavakara Upanishad) by F.Max Mueller.
http://www.realization.org/page/namedoc0/kena/k_0.htm
The Upanishads
Introduction to the Upanishads with comments on individual Upanishads.
http://www.kheper.net/topics/Upanishads/index.htm
The Upanishads
A translation of 11 Upanishads by Swami Nikhilananda.
http://sanatan.intnet.mu/upanishads/upanishads.htm
Upanishad
Isha, Katha, Kena, and Maitrayani Upanishads in HTML and Pdf format. Also a brief introduction to Upanishads.
http://www.gatewayforindia.com/upanishad/upanishads.htm
Hinduwebsite: Upanishads Home Page
Presents original English translations of several Upanishads, writings, commentaries and essays on the philosophy of the Upanishads
http://www.hinduwebsite.com/upaindex.asp
