They start shipping this week.
Contrary to what ToddA was saying, the 2.16ghz Yonah is available but as an upgrade. I think the 2.16ghz is not available in a basic model as it would make the cost of the MacBook prohibitive. So, instead Apple is offering the fastest and greatest Yonah as part of an upgrade instead.
http://www.theinquirer.net/?article=29694
