Excellent suggestions on a DIY spam filtering solution on Instructables: “I have been using a method of spam filtering for a number of years that works well in sorting personal communication from channels that may induce spam. I generally issue one email address to personal contacts and a second is used when dealing with online forum, e-commerce etc where I expect that address will fall in to the hands of spammers. I have setup two gmail accounts and the ‘spam’ account forwards all mail to the ‘personal’ account which labels those received mails with a filter accordingly. By pushing spam filtering out to the edge of the mail client, the address, you take away reliance on spam filtering technologies which can be duped.” Link.
HOW TO – Improved spam filtering