List of web hosting control panels

Ajenti (website) License: LGPL
AlternC (website) License: GPL
ASM (Account Services Manager) (website)
BoxCtrl-SE (BoxCtrl Server Edition) (website)
DTC (Domain Technologie Control) (website) License: LGPL
EHCP (website) Open Source
OpenPanel (website) Open Source
fosvm(Supports Single Server only)([1])
ISPConfig (website) License: BSD
ISPcp Omega VHCS fork (website) License: GPL-2
Kloxo Previously LxAdmin (website) Free Open Source, License: AGPL V3
RavenCore (website) License: GPL
SysCP (System Control Panel) (website) License: GPL
VHCS (website) - How-to install for Debian - (3.1) - (4.0) License: Mozilla license (not so free...)
VishwaKarma (website) License: GPL
web-cp (website) License: GPL
Webmin (website) License: BSD like
ZPanel — Windows and Linux (website) License: GPL
GNUPanel (website) License: GPL

Commercial panels with limited free version (not trial versions)

CONTROLzx (renamed from Drzes) (website)
DigiPanel (website) No longer active.
Parsv — Windows (website)
ServerPilot (website)
VirtualMin — addin module for webmin, comes as a free version or a paid version with more features (website)
XUnitconf(website)
Zervex — Linux (website)