(Originally posted 2003.Jun.14 Sat; links may have expired.)
Reading the book Lean Development by Mary and Tom Poppendieck has reminded me that successful group-improvement comes from self-directed (self-improving) groups -- and that the principle of self-improvement is more important than the specific practices.
They have an example of a software team within a large company that decided to improve their own processes. That improvement was noticed, and a committee formed to copy their improved practices to other teams in the company -- which never worked as well for those other teams as it did for the first team.
They also say the same thing happened (is happening) as NUMMI - the auto plant owned by GM and run by Toyota. Originally it was GM's worst plant, but within a year of Toyota taking over its management, it became one of GM's most productive plants — low absenteeism, high quality (almost as high as Toyota's plants) — with substantially the same people. GM tried to copy the practices to other plants, never with much success. The principle of continuous, self-directed-improvement is what makes NUMMI different, and which GM doesn't seem able to copy.