Zint Barcode Generator is a free open source software application that can generate professional quality barcode images for printing or embedding into documents. It supports a wide range of barcode formats including Code 128, Code 39, EAN/UPC, QR Code, Aztec Code, Data Matrix, and PDF417. It also supports outputting barcode images in a variety of formats, such as SVG, EPS, PNG, and TIFF. The software is designed to be easy to use, with an intuitive graphical user interface and a comprehensive set of customization options. It is also highly portable, and can be used on Windows, Mac, and Linux systems.
Discontinued is not compatible with newer versions of Firefox, etc.: https://addons.mozilla.org/en-US/firefox/addon/OfflineQR/