Links

Examples

Here are projects I've released with source code folded with Code Browser:

A simple OpenDocument Viewer written in C++.
An XML parser written in assembly. Code Browser is especially useful for assembly programming as it helps to add a structure to a very flat language.

Copper

Copper is the programming language used to write Code Browser.

Code Folding

Description of Folding - An introduction to folding by Andy Key, the author of the Andy's Editor.
What is a folding editor? - Another introduction to folding editors by Michael Haardt, the author of fe.

Other Folding Editors

Few more editors supporting explicit folding (i.e. not based on syntax or indentation):

SciTE supports both implicit and explicit folding (at least for C/C++ using //{ and //}).
jEdit is a text editor for programmers that support folding based on indentation or explicit folding.
Vim. Vim 6 introduces folding. It has six methods to select folds, including one to select them by markers.