Geany is a text editor using the GTK2 toolkit with basic features of an integrated development environment. It was developed to provide a small and fast IDE, which has only a few dependencies from other packages. It supports many filetypes and has some nice features.
Code Browser is a folding and outlining editor for Linux and Windows.
The editor is between a traditional text editor, a smalltalk class browser and a web browser like mozilla. It displays a structured text file (marker-based folding) hierarchically using multiple panes.