I just ran across Software Advice's explanation of lean, six sigma, and flexible manufacturing here. I suspect that some of the more knowledgeable lean folks will have plenty to quibble about: for example, there's no mention of respect for people; lean is actually about improving (not maintaining) quality; and there's nothing about problem solving and learning. But that's looking at the glass half-empty. The half-full part is that he avoids all the jargon, acronyms, and Japanese buzzwords that can be so off-putting if you're not one of the cognoscenti. Instead, you get an easy to read, one-page summary of a very important topic.
If you -- or your boss -- doesn't know much about lean, and you're trying to communicate the essence, this is a really good resource. By all means keep the Wikipedia bookmark, but add this one as well.