General :
HMG :
OOHG : Object Oriented Harbour GUI
Harbour :
Common :
Programación Harbour (by Miguel Angel Juárez Apaza)
The Oasis: the largest file archive for Clipper and x-Base on the web
HMG Page by Pepe Ruano (Spanish)
The Holmes’s Clipper Page : Useful infos on Clipper
Various sources for Harbour Minigui
From CA-Clipper to Windows in 5 Minutes
Clipper to Harbour – A Visual Tour by Pritpal Bedi
Harbour MiniGUI Lights (Portugues)
Windows
Other :
MinGW : Minimalist GNU for Windows
Crimson Editor : A professional source code editor for Windows.
Notepad++ : a free source code editor
PSPad : a freeware programmer’s editor
UPX : The Ultimate Packer for eXecutables
Inno Setup : A free installer for Windows programs.
GTK : A multi-platform toolkit for building graphical user interfaces.
Groups and mailling lists :
Harbour Project users’ mailing list
Harbour Project developers’ mailing list
Harbour Community in Google Plus
xMate : a freeware project manager and builder
Harbour MiniGUI (HMG) En Español
Grupo ooHG : Minigui compatible Graphic Library, class based and oop programming
MiniGui Rutinas : Grupo para compartir cualquier tipo de rutinas de Minigui extended, HMG, OOH
Oficial mailing list: Marinas-GUI
Documentations :
Clipper:
Harbour:
Download / Install
How to build harbour for windows
Language references
Great guides and Tutorials by Giovanni Di Maria
HMG
There are multiple news, discussion and mail groups about Clipper, Harbour and HMG. Surely, if you search, you will find more convenient to your needs. There are also a lot of individual web sites where you can obtain useful information on the subject.