I created a restaurant app for my client with zapable. it just took 30 minutes to get it live and I earned $459 from the client. it's really great learning.
King of App - King of App is an open-source mobile app builder.
draw.io - Online diagramming application
Stackify Retrace - Stackify Retrace is an application performance management platform for .NET and Java developers.
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.
Recast.AI - Recast.AI is the leading platform to build, connect and monitor bots.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.