ZXing - Barcode Scanner for Android
QR Droid - QR Droid Zapper
QuickMark - QuickMark makes everything possible.
Barcode & QR Code Scanner - A free app which allow to read and generate barcodes for Android.
Kinoni Barcode Reader - Use your iPhone as a professional barcode scanner for your PC or Mac.
MKH Barcode Reader - This tool can be used to scan QR codes on your PC or tablet. Note: a webcam is required.