yEd is a free general-purpose diagramming program with a multi-document interface. Developed by yWorks
License: Free
Gliffy is user-friendly and excels in collaboration, making it suitable for teams working in real-time, while yEd Graph Editor offers advanced capabilities for complex diagrams and is better suited for users needing detailed graphing tools. The choice between them depends on the user's specific needs for simplicity versus power.