Meazure - What are the dimensions of that image? How big is this window?
On-Screen Ruler - lightweight, free, semi-transparent ruler
Bluegrams Screen Ruler - A lightweight and configurable ruler tool for Windows Desktop.
MentorCruise - Personalized mentorship experiences
Mimir - A modern podcast listening app built from the ground up for macOS to provide an intuitive, powerful, and feature rich podcast listening experience.
Pixus - Pixus is an AIR pixel ruler application, a handy tool for web and interface designers.