Does your team have a project manager? Probably. An iteration manager? Maybe. More likely not. Do you need one? What's the difference?
Google for "project manager vs. iteration manager" or similar phrases and you will get lots of job search links and about half a dozen fairly good articles and posts that attempt to answer these questions. (A selected few are at the end of this post.)
Probably the one that does it best is the original description from 2000 by Cara Taber and Martin Fowler: Planning and Running an XP Iteration ( http://bit.ly/YnnASZ )
In the section on team structure, they give a real-world example that makes the inward-facing, outward-facing nature of the two roles pretty clear. Their description shows that making these roles effective for the team is not so much about how you characterize tasks but how you enagage personalities for situations. That has certainly been my experience. Across all my projects, going back to the 1990s, projects with teams larger than five ran best when two or more people split up the PM and IM roles.
The PM role primarily looks outward and deals with leadership from participating teams and the overall parent company organization. The IM role looks inward and tracks the pulse of the team, resolving small issues and escalating big ones, and keeping the metrics clean.
You can compare it to film-making. The PM is the Producer and the IM is the Director. Sometimes a Producer can direct their own film or a director will self-produce their work but the results are generally better with a team.
The Producer is responsible for backing and selling the project vision, plus all of the arranging of people, places, supplies, contracts, etc. necessary to bring cast, crew, and location(s) together. The Director is responsible for conveying the creative vision to the cast and crew and enabling them to perform the actions that become the film. (You can make the same type of analogy with sport team owners and coaches, or the difference between conducting an orchestra vs. the executive duties of a music director.)
The Software Project Manager, like the Producer, is the big-picture, big-structure, studio-boss facing, investor-facing money person.
The Iteration Manager, like the Director, is the on-scene, every day, fine-tuning, people-relating, situation-improvising person.
If the software project is large or complex enough, the IM role can be full-time. More likely it is not. Sometimes the PM and IM role is combined in one person but more often the IM role is played by a BA, QA or Dev Lead, or a combination of people in those roles.
The reason why that happens, it seems to me, comes down to personality type – there are Manager types and Maker types ( http://bit.ly/WZOYHc ). Project Managers obviously tend toward the Manager type. BAs, QAs and Dev Leads tend toward the Maker type. For whatever reason, IMs (at least all the ones I’ve met) also tend toward the Maker type.
Perhaps there is a flow-state awareness that happens to Maker-types that makes them better attuned to the day-to-day rhythm of the team. Whatever it is, it seems different from what drives Manager types and all teams need some of each.
A few more links
Venkatesh Krishnamurthy, The Differences between a Project Manager and a ScrumMaster. http://bit.ly/14NuFAe
Darian Rashid, Transforming a Traditional Manager into an Agile Manager. http://bit.ly/Y5H7Z7
Rene Maslen, What is an Iteration Manager and why do we need one? http://bit.ly/WZu634
Petra Skapa, Iteration Management: Unclogging your development process. http://bit.ly/YdmWe1