OmniGraffle is described as 'can help you make eye-popping graphic documents—quickly—by providing powerful styling tools, keeping lines connected to shapes even when they’re moved, and magically organizing diagrams with just one click' and is a well-known app in the Office & Productivity category. There are more than 50 alternatives to OmniGraffle for a variety of platforms, including Windows, Mac, Online / Web-based, Linux and iPad. The best alternative is diagrams.net, which is both free and Open Source. Other great apps like OmniGraffle are Pencil Project (Free, Open Source), yEd Graph Editor (Free), LibreOffice - Draw (Free, Open Source) and Dia (Free, Open Source).
CADE is a compact but powerful 2D vector editor for Windows. It includes basic Microsoft Office Visio functionality and could be used to create diagrams, network diagrams, flowcharts, schemas, maps and so much more.
Thortspace builds a 3D space-map of your thoughts. The 3-D linkages generated by Thortspace spheres facilitated both new insights and new lines of data management, and – almost magically. Thortspace is an invaluable aid to brainstorming prediction.
Core2D is a multi-platform application for making data driven 2D diagrams. The application has built-in wyswig vector graphics editor where you can bind data to shapes, share data across multiple documents, edit documents using layers.
Merge Plan is a user friendly diagram application. It is fully compatible with most diagram file formats. It is a great value in comparison to other diagram applications. It is part of Merge Soft Office.