draw.io - Online diagramming application
Codespace - A beautiful cross-platform code snippet manager
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.
CodeMyUI - Handpicked code snippets you can use in your web projects
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Hasty - A fast code snippet generator for WordPress