Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
NAPS2 - NAPS2 is a document scanning application with a focus on simplicity and ease of use.
Capture2text - Capture2Text enables users to quickly OCR a portion of the screen using a keyboard shortcut.
Simple Scan - Project information. Part of: The Gnome Project. Maintainer: Simple Scan Development Team. Driver: Simple Scan Development Team. Licence: GNU GPL v3.
ksnip - Ksnip is a Qt based cross-platform screenshot tool that provides many annotation features for your screenshots. - DamirPorobic/ksnip
XSane - A good proposal for SANE-2 has been written.