I tripped over some interesting technologies that are up and coming in the battle against SPAM...
SPF appears to be the more promising of the three major 'competing' SPAM answers. I am considering registering SPF entries in my DNS.
Microsoft has a Caller ID proposal.
And Yahoo! has partnered with Sendmail to bring DomainKeys.
I have to read more technical specs before I make a final decision on which of these initiatives gets my support ... however at this point, SPF is the frontrunner.