The Anti-Phishing Working group site is an excellent resource as it contains details of everything you (OK most people!) could ever want to know about Phishing.
The site includes an interesting paper titled "Online Identity Theft: Phishing Technology, Chokepoints and Countermeasures".
Another interesting link is to the "InternetPerils Online Visualization Technology" which apparently "Actively Tracks and Pinpoints Phishing Websites" - I've not heard of this before and am intrigued.
Thanks to Jules for pointing the Anti-Phishing site out to me. It was quite funny (to me at least!) that when she asked me where to find out more about Phishing I was wearing a GetSafeOnline sweatshirt and was able to point at the address written on it! From there she followed the GetSafeOnline site guidance and found the Anti-Phishing website.