How can I find a comprehensive list of all English words?

This site links to a few major word lists.

Scrabble Dictionary

The complete Oxford Dictionary of the English Language.

www.oed.com but they charge for access.

Welcome to fluther!
I’m sorry you can’t find what you’re looking for, but it turns out there is no such thing as a comprehensive list, because English, like all living languages is fluid and always changing. We, as an English-speaking community, consider the Oxford English Dictionary to be the best possible approximation of all words, and thus the authoritative list. Unfortunately for you, it is a dictionary, not just a lexicon, so it does include definitions.

OED editor-at-large Jesse Sheidlower explains why we cannot agree on a comprehensive list of all English words:
http://www.slate.com/id/2139611/

Excellent article, morphail! You and I always seem to answer these oxford english dictionary-related questions, and in similar ways, too. We are really on the same page! (get it? ah, i crack myself up…)

I always liked those HUGE dictionaries the libraries have.