Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
DisplayFusion - DisplayFusion will make your multi-monitor life much easier.
Capture2text - Capture2Text enables users to quickly OCR a portion of the screen using a keyboard shortcut.
WindowGrid - Quickly and easily layout windows on a dynamic grid using just the mouse.
ksnip - Ksnip is a Qt based cross-platform screenshot tool that provides many annotation features for your screenshots. - DamirPorobic/ksnip
Mizage Divvy - Divvy is an entirely new way of managing your workspace.