Unix

CLEX File Manager
Text based file manager for UNIX systems. Free source code distribution.
http://www.clex.sk/

FLFM
Fast Light File Manager. A small graphical file manager for X-Windows based on the FLTK library. Xdnd 4 compatible. GPL.
http://oksid.ch/flfm

KCommander
Linux Windows Commander style filemanager. Open Source.
http://www.kcommander.org/

KNC
Graphical 2 windows file manager for KDE. Download source.
http://software.freepage.de/stormer/

The NewSyslog Project
Newsyslog is a highly configurable program for managing and archiving log files (such as those produced by syslogd).[Unix or Unix-like system]
http://www.weird.com/~woods/projects/newsyslog.html

The Unix Cockpit
Open Source file manager for X11/Unix, runs under almost any Unix flavour.
http://www.klagges.com/uc.html

UnixTree
XTree-alike console mode filemanager for Unix and Linux systems. History, tips and tricks, guided tour. Freeware.
http://www.unixtree.org/

Ytree
A Unix (curses-based) file manager similar to DOS Xtree for browsing filesystems and archives. Open Source.
http://www.han.de/~werner/ytree.html