NAPS2 - NAPS2 is a document scanning application with a focus on simplicity and ease of use.
Docr - Docr is a free app for the iPhone smartphones that lets its users scan all of their documents into sharp images and, in the end, store them as PDF files.
Simple Scan - Project information. Part of: The Gnome Project. Maintainer: Simple Scan Development Team. Driver: Simple Scan Development Team. Licence: GNU GPL v3.
Scanner Pro - Scanner Pro turns your iPhone into portable scanner in your pocket.
XSane - A good proposal for SANE-2 has been written.
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.