http://thoughtsofanidlemind.wordpress.com/2012/03/28/dmarc-spf/
Domain-based Message Authentication, Reporting & Conformance:
http://dmarc.org/
Sender Policy Framework:
http://www.openspf.org/
Email Resource and Delivery Tools Site:
http://www.unlocktheinbox.com/DMARC Wizard:
http://unlocktheinbox.com/dmarcwizard.aspx
DNS Lookup Tool, Reverse DNS Lookup Tool:
http://www.dnswatch.info/
Whitelist Provider for Email Filtering:
http://www.dnswl.org/
Beveridge Tools:
http://tools.bevhost.com/