Nielsen Norman group just published a 95-page report about Agile processes, and how design can work inside the flow. I haven’t had the time to read through the whole thing yet, but it seems the overall quality of the papers is pretty good. The report starts with a fairly long bit about agile scrum-style iterative processes and delves into the design bits only later, so even if you’re not actually using agile processes right now, the paper should fit you just fine.
I’m not getting a dime out of recommend the thing – the reason I’m pointing you there is that UX and Agile is not necessarily the easiest marriage in the world, and that I’d love to see more companies start using Scrum. I just watched the team give a sprint demo today back at the office, and it’s glaringly obvious people are happier now than what they were before we started using Scrum. And we’re getting more done, too! :)