Open Food Facts
Open Food Facts, a free database of food products.
The data (mainly ingredients and nutrition facts, also packages, labels, locations, shops and pictures) is under free licenses (though written down from packages) and can be downloaded.
The server software source code (Perl) needs to be rewritten before it can be published: http://en.wiki.openfoodfacts.org/Project:Product_Opener#Introduction
The most obvious feature of that software is to calculate average nutrition facts and compare the nutrition facts of a product to those of its categories (e.g., compare a yogurt to all yogurts or to all dairies). It can also make graphs.
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