ScanTailor - Scan Tailor is an interactive post-processing tool for scanned pages.
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.
YASW (Yet Another Scan Wizard) - Download YASW for free.
Scanner Pro - Scanner Pro turns your iPhone into portable scanner in your pocket.
PDF Scissors - Crop pdf. Drop margin, whitespace. Auto crop all pages. Easy feature to make nice cropped pdf for ebook readers such as Amazon Kindle, Sony, Cybook etc.
Genius Scan - On The Go.