According to this job listing on Craig's List, Google is fostering internal start-ups called Googlettes. While Google doesn't seem to be talking publicly about them, word on the street is that these may be the basis Google's strategy for managed growth.
Rather than becoming huge like a Yahoo! or an AOL, Google itself will incubate more start-ups from within, building on the stability of the current king of all search engines while keeping innovation and flexibility at the forefront.
Could it be that the buzz-generating Google calculator was the result of one of these Googlettes?