bcWebCam - Scan barcodes and QR Codes with your computer web cam
ZXing - Barcode Scanner for Android
QR Droid - QR Droid Zapper
QuickMark - QuickMark makes everything possible.
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
Kinoni Barcode Reader - Use your iPhone as a professional barcode scanner for your PC or Mac.