I saw a good talk on this recently. Basically this team started off doing a fairly standard Scrum process, then transitioned to Kanban and Lean. One of the most important things they did was to gradually erode the distinctions between testers and developers. Testers were involved in writing unit tests and code, developers were bringing in more higher level tests early in development. It was a steep learning curve for the testers, but worth it as the team was building in quality from the start. By now the testers call themselves developers because their work is so integrated in the process of writing code.
