Back in November 2010, I wrote an eBook about progress metrics for the Seapine Agile Expedition. This eBook discusses useful metrics for Agile projects and gives insight into some traditional metrics that have fallen out of favor with the adoption of Agile methods. For more information, read "Measuring Up: Progress Metrics".
There is also a supplementary blog post on The Seapine View that talks about how to move away from percent complete. This often misunderstood and misused metric is still alive and well in many organizations today, but yields little value in the way many people think it does. Read "How to Get Away from Percent Complete" to find out more.