One of the things we routinely struggle with when it comes to retrospective time is building a timeline of what everyone did and the difficulties and successes we experienced.

Even though we use Microsoft's TFS to capture individual work item tasks we have found it difficult to reconstruct a view of the sprint that is more fine grained than product backlog items but not as detailed as invidual sprint backlog items.

Once it was identified as an issue, we undertook a number of experiments:

• Sticky notes on a board that fell off when someone walked past
• Pinned notes on a board which stayed put but were hard to move around.
• Gantt charts in MS Project (well, it's Project for one thing).
• Trawling through individual TFS items to reconstruct the month.

Nothing seemed to exactly match what we felt we needed and was either too heavy-weight or just plain got in the way. At the start of the last sprint we discovered a tool called Trello and decided to try experimenting with it during the sprint.

Trello is a simple, one page browser-based application that supports team collaboration in the style of a virtual Kanban board. It's developed by Joel Spolsky's company, FogBuzz, who are actively using it in their projects to track work and have several public boards you can use to see the full power and flexibility of the platform.

The general idea is the screen is split into three columns - not done, doing, done - you create cards to represent work and assign them to the appropriate column. As work progresses, you can drag the cards between columns and assign ownership among the team members to track who's working on what task.

Cards move through the columns until at the end of the sprint everything should arrive in the "done" column. The application uses a realtime update mechanism so a change made by one team member immediately gets pushed to all the others.

The way our team uses Trello is to set up a blank board for each sprint. As team members pick up PBIs from TFS, we create new cards as required to track general themes in our work. Where PBIs are measured in days or weeks of effort and SBIs are generally measured in hours, we found creating cards that grouped together several related PBIs to work best.

At the end of the sprint it was easy to see, in order, how the sprint had progressed and we found that a normally difficult part of the team retrospective was sped up significantly. Probably the best endorsement of the tool came at the end of the retrospective when it was unanimously decided to keep using it for now on.

The technology used by Trello is described in a blog post if you are interested in how such a wonder was built.