Scanner Pro - Scanner Pro turns your iPhone into portable scanner in your pocket.
ABBYY FineReader - ABBYY's latest PDF editor software, FineReader 16 you can easily convert files like PDF to Excel, PDF to Word, edit, share, collaborate & more with this PDF editor!
Scanbot - Scanbot is a mobile app that allows you to use your device's camera as a document scanner. The app is capable of scanning a large number of source materials, and it can handle QR codes as well.
Tesseract - Tesseract is an optical character recognition engine for various operating systems
Genius Scan - On The Go.
GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.