LilyPond editor based on JEdit, implemented as a JEdit plugin. It is an edit mode and a feature rich plug-in, which provides tools for making LilyPond scores. Features include instant completion, error report, PDF preview.
The NightLabs PDF Viewer is an Eclipse plug-in for viewing PDF files in Eclipse-RCP-based applications. It contains Eclipse UI components (like a 'Composite' or an 'Editor') for the easy integration into your own program and a stand-alone viewer app.