ZXing - Barcode Scanner for Android
bcWebCam - Scan barcodes and QR Codes with your computer web cam
QuickMark - QuickMark makes everything possible.
QR Droid - QR Droid Zapper
NeoReader - The NeoReader is a universal barcode scanning app that transforms your mobile phone into a barcode scanner, allowing access to mobile web content by scanning codes from virtually any medium
Barcode to PC: Wi-Fi scanner - Turn your smartphone into a real barcode scanner