Google - Language tools
Contains a beta machine translation tool. The page will also give you access to all the localized and in-country google sites as well as allow you to do searches with a language filter.
http://www.google.com/language_tools?hl=en

Guidelines for Writing Content that Will Be Machine-Translated [This link generated an error during the last automatic check]
These guidelines where written for IBM's WebSphere Translation Server users but are applicable to anybody wishing to produce content that will undergo machine translation.
http://publib.boulder.ibm.com/voice/pdfs/white_papers/MT_Guidelines.pdf

Should I use machine translation?
Alan K. Melby provides guidance on when to use machine translation.
http://www.ttt.org/theory/mt4me/index.html

WebSphere Translation Server : machine translation demo
Online demo of IBM's machine translation solution which allows you to translate any webpage. The demo allows to translate English content into French, German, Italian, Spanish, Korean, Simplified and Traditionnal Chinese, Japanese. German, Spanish and Italian contant can also be translated into English.
http://www-4.ibm.com/software/speech/translation/demo/

Why Can't a Computer Translate More Like a Person?
Alan Melby shows in this lecture the limits of machine translation. While written in 95 the article is still very much up-to-date.
http://www.ttt.org/theory/barker.html

WorldLingo - Machine Translation Services
WorldLingo provides a variety of Machine Translation services for German, French, Italian, Spanish, Portuguese, Dutch, Greek, Russian, Chinese, Korean, and Japanese. Can translate URL or text samples.
http://www.worldlingo.com/products_services/worldlingo_translator.html