Open Food Facts
Open Food Facts (world.openfoodfacts.org) is an open database and associated app (Android, iOS, Windows Phone) and webservice of food products initiated in 2012 by French programmer Stéphane Gigandet. It is limited to foodstuffs only by the contract, other will be removed and clearly seeks not to be political.
The database is copylefted under w:Open Database License, database entries under Database Contents License and the uploaded photos under CC-BY-3.0 Creative Commons so the database and the photos can be re-used in other services so it would seem a good place to contribute.
Information verification is based on photos of the labeling on the package. Adding information not featured on the label seems to be forbidden, probably to avoid legal threats.
Wikipedia on w:Open Food Facts