PhishTank is a free public database of phishing URLs where anyone can submit their phishes via email or through the website.
The submissions are verified by the other community members who then vote for the suspected site.
This is such a neat idea as sites can be categorized just based on user feedback without even having to manually verify each and every submission.
PhishTank employs the "feedback loop" mechanism where users will be kept updated with the status' of the phish they submit either via email alerts or a personal RSS feed.
Naturally, once the PhishTank databases grows, other sites can harness the data using open APIs which will remain free. OpenDNS would also use this data to improve their existing phishing detection algorithms which are already very impressive and efficient.
PhishTank | PhishTank Blog [Thanks Allison]
Related: Google Safe Browsing | What is Vishing ?