There's also The Wordlist Project. It appears to have moved to http://www.gattinger.org/wordlists/.

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"I just read perlman:perlboot," said Tom, objectively.
naChoZ

Update: Aug 21

Stumbled upon this link. It contains a smaller but still useful wordlist. About 80,000 real words, all caps, no spaces, eight letters or less. This could be very useful for simpler purposes that wouldn't require the Wordlist project's 600,000+ word list.