There’s a specific agile tool which I think every early-stage product team should use, regardless of whether they’re following the Lean Startup methodology. Lean Startup drew its roots from agile software development. Eric Reis added Steve Blank’s idea of customer development to agile. Assuming we aren’t talking about re-reading Eric Reis’ book for the 17th time, the best Lean Startup tool is the dogeared post-it.
What? Why not some kind of fancy-shmancy online tool that defines, builds, and releases your product? In your sleep. There’s lots of those around. < grin >