Launch an external diff tool like WinMerge in Eclipse
EditBox is the Eclipse plugin for source code background highlighting.
Open-source plugins included in the distribution of IntelliJ IDEA
Literate programming for eclipse
Light-weight Scintilla-based text editor with syntax highlighting
a DSL for type systems, reduction rules, interpreters for Xtext langs
Graph algorithms interpreter, IDE, debugger, 3D visualizations.
Cloud-based Integrated Development Enviroment
JetBrains Meta programming System
Eclipse integration for Isabelle proof assistant
An Eclipse plug-in for the IBM FileNet P8 Content Engine and CMIS