Wordnet Online: http://wordnetweb.princeton.edu/perl/webwn
The most recent Windows version of WordNet is 2.1, released in March 2005. Version 3.0 for Unix/Linux/Solaris/etc. was released in December, 2006. The version 3.1 database files only (no code) can be downloaded and substituted for the 3.0 files in applications and with WordNet’s Unix/Linux application. Version 3.1 is also available when using the online interface.
Download the latest WordNet packages, including the Prolog version and sense mapping files.