Great website located at http://www.accesstoinsight.org with a huge collection of information about Buddhism, particularly Theravada Buddhism. Contains a large number of translations of the Pali cannon, as well as collections of talks an essays by monks from the Thai Forest Tradition, and reprints of texts from the Buddhist Publication Society.
ATI is a great reference source- the scriptures and other texts collected there are indexed by name, subject, and Pali name, and there are also indices of proper names, and a search interface provided by Google.
The collection focuses primarily on the Sutta Pitaka, but information on all three segments of the tipitaka are available, including translations and explanations of the monastic code (Patimokkha).
ATI started life as a bbs for folks interested in Buddhism running out of Massachusetts, and continues to be run privately by its founder, John Bullitt. From its earliest days, if has supported a traditional Buddhist notion of openness that would sound quite familiar to most free software advocates. All of the texts available can be freely re-distributed and re-formatted, providing that no one charges for their use. As a result, ATI texts can be found in quite a few spots on the web- the official site of the Sangha in Burma was basically no more than a mirror of the site, at one point.