Recommended SpamAssassin update channels?
See http://wiki.apache.org/spamassassin/SareChannels, especially the dostech channels.
About the only resource that seems to stay current with SpamAssassin is spamtips. Check out their Ultimate Setup Guide - http://www.spamtips.org/p/ultimate-setup-guide.html
Specifically, the "Sought Rules" http://wiki.apache.org/spamassassin/SoughtRules is the channel I'm recommending.