As the field of ESP is vast, there are a large number of websites with ESP relevant material.

The IATEFL ESP website has information about the SIG, its events and conferences and its Newsletter: http://espsig.iatefl.org/

Damian Rivers' English Language Resource Website has a section on ESP with lots of useful resources and links for ESP teachers and students: www.eapstudy.com

Information about the UK ESOL for Work initiative can be found at: http://www.dfes.gov.uk/readwriteplus/ESOL_for_Work

The following website has links to resources for teachers and learners in a number of disciplines: http://www.rong-chang.com/esp.htm

The website of Barney Barrett and Pete Sharma includes links to lots of useful websites for ESP teachers:
http://www.te4be.com/pages/mat4learn/links/links_esp.htm

The yourdictionary.com website has links to dictionaries and glossaries of specialised words in the English language:
http://www.yourdictionary.com/specialty.html

Arlyn Freed's ESL/EFL ESP website has links to a large number of specialism specific resources:
http://www.eslhome.com/esl/esp/

The IATEFL ESP SIG's Discussion list moderator can be contacted at: w.nash@sheffield.ac.uk

The yahoo group of the IATET (International Association of Technical English Trainers) can be accessed at: http://www.esp-world.info/index.html