ZXing - Barcode Scanner for Android
TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.
Barcode to PC: Wi-Fi scanner - Turn your smartphone into a real barcode scanner
GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
bcWebCam - Scan barcodes and QR Codes with your computer web cam
Yandex.Images - search for images on the internet, search by image