draw.io - Online diagramming application
ifttt - IFTTT puts the internet to work for you. Create simple connections between the products you use every day.
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
Zapier - Connect the apps you use everyday to automate your work and be more productive. 1000+ apps and easy integrations - get started in minutes.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
n8n.io - Free and open fair-code licensed node based Workflow Automation Tool. Easily automate tasks across different services.