ZXing - Barcode Scanner for Android
SecScanQR - The QR-Code Scanner/Generator that cares about your privacy
MKH Barcode Reader - This tool can be used to scan QR codes on your PC or tablet. Note: a webcam is required.
QR Droid - QR Droid Zapper
QuickMark - QuickMark makes everything possible.
Binary Eye - Binary Eye is a Free Open Source barcode reader/scanner and generator.