Necromancer's Dos Navigator is a "Norton Commander" clone. It uses a well known text-mode interface, is highly customizable, and has a lot of features. Its key features are a text editor with syntax highlighting, horizontal/vertical blocks, multiple codepages, undo/redo, bookmarks, powerful searching, and regex; a file viewer with text view, asm/dump/hex edit, raw blocks, header viewer, search, regex, and unlimited filesize; a powerful filepanel with higlighting, VFSs, and filefind with textsearch and regex; a calculator; and more.
OwenShow is an open-source file browser demonstrating various techniques/failures in Borland Kylix/Delphi code, including fork, drop/drag, and much more. Unlike other browers, directories are scanned explicitly and, if desired, to full depth, i.e. to get detailed descriptions of directory trees. Finding directories/files is supported by inexact/exact cumulative search.