Java editing tool with support for syntax highlighting
Scintilla is a source code editing component and tiny IDE for Win32 and GTK+.
Open source web-based source code editor for your Mac
Frontier Kernel – High-performance Web content management, object database, system-level and Internet scripting environment
Araelium Edit – General purpose software development application
Chamo is a source code editor, even if it can be used to edit any text file.
D4Xcode is an application that will offer support for editing D source code files using the Xcode IDE on Mac OS X