Meazure - What are the dimensions of that image? How big is this window?
Teachable - Create and sell beautiful online courses with the platform used by the best online entrepreneurs to sell $100m+ to over 4 million students worldwide.
Bluegrams Screen Ruler - A lightweight and configurable ruler tool for Windows Desktop.
Clever - syncing between education applications for K-12 schools
On-Screen Ruler - lightweight, free, semi-transparent ruler
Claroline - Claroline is a collaborative eLearning and eWorking platform.