On-Screen Ruler - lightweight, free, semi-transparent ruler
MyBrocard - Brocard allows you to create an unlimited number of virtual cards for paying for advertising and other online payments, manage a team of buyers, choose from 20+ bins for various tasks, and enjoy convenient API for integrations.
Meazure - What are the dimensions of that image? How big is this window?
Coinramp - The Coinramp Card lets you spend over 10+ cryptocurrencies like cash, online, in-stores and ATM withdrawals. Available in 100+ countries, no ID needed. Anonymous Crypto Cards
Bluegrams Screen Ruler - A lightweight and configurable ruler tool for Windows Desktop.
PST.NET - Virtual payment cards for online shopping and advertising