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Chris Santerre has a collection of custom rules available at the SpamAssassin Custom Rule Emporium - http://www.rulesemporium.com
The Hebrew SpamAssassin rules project is located at http://www.deltaforce.net/hebrewspam
There's an additional SpamAssassin wiki at http://www.exit0.us . This wiki seems more focused on rules and includes a German Ruleset.
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