Google Labs is naturally well-known, but Gmail Labs is something new. Google announced today that it will release this "feature" on June 5th. In fact, it can't really be called a "feature"; I'd rather call it an opportunity to participate, as this initiative aims to involve users in the development of Gmail. Google's "20% free time" plan is also very famous; every Google engineer has one day of free time out of the five workdays in a week to develop any projects that interest them.