Encyclopedia of Life (EOL): http://www.eol.org/
An ambitious project to publish online, and collate from other web-sites, all the information relating to the 1.8 million named species so far published.
The project includes WIKI pages where anybody can contribute. In due course these will be vetted by experts and incorporated into the main body of the site.
Because of its international nature, the English browser may find many of the "English" names unfamiliar.
The first set of authenticated species pages are expected by the middle of 2008.