In a recent two-part article, Jeff Patton discusses how to bring a user experience design process into an Agile world. It's got some great actionable suggestions and I recommend it as a good summary of UX and Agile.
This article also relates to a project that I am currently working on. We are trying to be as "agile" as possible by building the shell of a website from the wireframes before design mockups haven started. We are also doing usability testing during development, and conducting walkthroughs every two weeks with the client so that we can test our progress. I have worked on other projects where we have tried to be agile, but this one (I am happy to find out) follows many of the suggestions in the article.
A couple points stood out for me as things we do not explicitly do though. We do not tend to conduct interviews with stakeholders and end-users during the development phase. We usually formally wrap up interviews during a discovery phase, but we do continue on with usability testing and "walkthroughs" later on to make sure that development is matching what the stakeholders/end-users envision. It would be interesting to work on a project where interviews continue throughout the project, and where research and validation happen at the same time as the article suggests.
Another interesting point is "prototype as a specification." At Habanero we may use a combination of wireframes, mockups and a document as a specification. However, I am experimenting more with building simple clickable prototypes in Fireworks, and this seems like an area we could exploit more on Agile projects. Documents tend to get stale pretty quickly and are hard to keep up to date — a prototype + discussion definitely seems like something that could be used to build concepts, and then the concept is kept "documented" through the actual code.
This is an interesting area — I would love to hear about any other methods people are using during Agile projects!