UX Flow Wireframe Prototyping System - Create beautiful user flows prototypes for your next project
Practice.dev - Practice programming for free
draw.io - Online diagramming application
CodeDammit - Learn programming by looking at real code examples
UMLGraph - UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.
Pre-Launch Widget Templates - 100+ widgets for your pre-launch campaigns