At the top of pages on the main site, the Search box goes to a Google search of site:http://www.arduino.cc/ and seems to exclude pages that should be at the top of the results. Once at Google, changing the search to site:http://arduino.cc/ seems more accurate.
For example, when searching for servo library, the user is redirected to a Google search of _**servo library site:http://www.arduino.cc/**_ the Reference page for the Server Library (Servo - Arduino Reference) doesn't show up on the first 5 pages of results (I didn't check beyond the 5th page). By changing the search to _**servo library site:http://arduino.cc/**_ the Servo library reference page is appropriately the first result.
I think the main site Search box should send the user to a search of site:http://arduino.cc/ (without the www.).