Sortable, Sticky Index Cards
My team (which is running a modified version of XP) is currently using sticky notes on the wall to track our work items and stories. We have a big area for all the project features. We use those giant (3 foot or so) sticky notes to hold a weekly iteration worth of work, and we archive the accomplishments of each iteration by stacking the current iteration on top of all the previous iterations. And all the sticky notes are color coded: blue for development, yellow for test, green for documentation, etc. This is a really simple system. (Of course, we are experimenting with a few changes to the system to see if we can improve on the amount of immediately available information, but more on that on another day.)
I was at one of the local office supply stores the other day, looking for a few more colors for a few more categories of work, and I saw these sortable, sticky index cards. These things are fantastic. The do not stick to each other, so you can stack them, sort them, handle them just like normal index cards, but they stick to the wall. Awesome. I'll be playing with them over the next couple of weeks to see how viable they are for use in our system.