In my article from 7/2009 on how to access your email (actually, any web service!) with challenge-response. The reason that you event want to do that, is to avoid risking your private password by typing it in a public computer.
I am currently working (on my limited free time) on an implementation of a Challenge-Response OpenID provider. When I thought of the idea, I searched the web, and found that a a group of students at Stanford had already done it. In my opinion, their solution (called Snap2Pass) is good, but hard to deploy (as it requires a chat server).
Additionally, Windows Live Mail has a nice (and simillar) feature: single use code.
My original article is attached below: TODO: attach the article in html