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