Top Alternatives to OmniGraffle

Lucidchart is a web-based application to draw diagrams.

draw.io is free online diagram software for making flowcharts, process diagrams, etc

Dia is free and open source drawing software.

yEd is a free general-purpose diagramming program with a multi-document interface.

XMind is the most professional and popular mind mapping tool.

Pencil Project is an open-source GUI prototyping tool.

Microsoft Visio (formerly Microsoft Office Visio) is a diagramming and vector graphics application and is part of the Microsoft Office family.

LibreOffice is a full-featured office productivity suite that provides a near drop-in replacement for Microsoft Office.

ConceptDraw PRO is diagramming software used to create business graphics, including ConceptDraw Flowcharting Suite.

Creately is a collaborative diagramming and design software used by teams around the world to communicate more effectively.

Balsamiq Mockups is a rapid wireframing tool that helps you Work Faster & Smarter.

Moqups is a streamlined and intuitive web app that helps you create and collaborate on wireframes, mockups, diagrams and prototypes for any type of project.

PlantUML is an open-source tool allowing users to create UML diagrams from a plain text language.

Google Drawings is a free, web-based diagramming software developed by Google.

Graphviz (Graph Visualization Software) is a package of open-source tools initiated by AT&T Labs Research for drawing graphs specified in DOT language scripts.

Gliffy is software for diagramming via a HTML5 cloud-based app. It is used to create UML diagrams, floor plans, Venn diagrams, flowcharts and various other kinds of diagrams online.

Adobe XD is a commercial vector user experience design tool for designing web apps and mobile apps

MindNode makes mind mapping delightful.

Gephi is the leading visualization and exploration software for all kinds of graphs and networks.

Axure RP is a wireframing, rapid prototyping, documentation and specification software tool aimed at web and desktop applications.

Grafio is a fun and capable diagraming app for iOS with plenty of features at a fraction of the cost of others.

Edraw Max is comprehensive mind mapping and planning tool network diagrams, floor plans, workflow diagrams, business charts, and engineering diagrams.

Umbrello UML Modeller is a free software UML diagram tool available natively for Unix-like platforms and Windows.

Mock up an application and show what's important, the idea, the information, the interaction.

Fluid UI is a browser-based wireframing and prototyping tool developed by Fluid Software and used to design mobile touch interfaces.

Diagram Designer is a vector graphics editor that allows you to create UML class diagrams, illustrations, flowcharts and slide shows.

Diagramo is an online flowchart software. It's FREE and Open Source ( GPL ) It's pure HTML5 Share and collaborate.

MockFlow is a collection of wireframe tools, prototyping tools, UI mockups, UX suite.

VisiTouch helps you view and convert to PDF your MS Visio diagrams for iPhone.

Nevron Draw is a software for creating flowcharts and diagrams.

Diagrammix is a tool for efficiently building attractive diagrams and flowcharts.