Useful Links:
1) QuakeC tutorials and documentation:
http://www.cataboligne.org/extra/qcmanual.html
http://pages.cs.wisc.edu/~jeremyp/quake/quakec/quakec.pdf
http://www.insideqc.com/qctut/
https://quakewiki.org/wiki/QuakeC_basics
https://quakewiki.org/wiki/QuakeC_tutorials
2) QuakeC tools:
FTEQCC is probably the most modern compiler available, with plenty of compilation options and enhancements. You can choose between GUI version and a command line version:
FTEQCC GUI (Win64)
FTEQCC (Win64)
More download options...
FTEQCC site with all downloads and documentation
3) Modeling tutorials:
http://pnahratow.github.io/creating-models-for-quake-1.html
One of the few good modelling tutorials available. There are some links within this document that explain how to create the QC for new monsters, as well as art tips and more.
4) Modeling tools:
QME is a modelling program for quake. It has some quirks and issues, but for the most part is usable. It's an "abandonware" so licensing is unclear atm. Author is unreachable. Here you have unpacked version without the installer (installer fails on modern systems).
MDL import/export plugin for Blender
2.79 /
2.8. It's not feature complete yet, but you can do quiet a lot with it. Easiest way to export MDLs if you know Blender (or you want to learn it)
Other download options and repository
here
QMDL /
FBXTOMDL /
MD3TOMDL are powerful model management and conversion utilities. They are written in Python, so it requires some knowledge of CLI.
Noesis is a GUI software that can convert from a variety of game and application formats into quake compatible formats.
5) Image/Skin/Sprite eitors:
AdQuedit is an app that allows manipulation and conversion of various quake formats. Most notably it is an easy way of changing skins on existing models. Also linked is the
manual.
"
FImg is an image editor for sprites and similar assets in Quake by FrikaC" -
Wiki
6) Pak tools:
Sometimes you want to extract assets from a pak file (PAK0, PAK1, etc.) You can use
qpakman for a command-line app or
PakExplorer for GUI equivalent.
7) Sound editing:
Ocenaudio - with a
tutorial from Dumptruck_ds
Wavosaur - different software, same workflow like above
8) Other:
Joshua "Skelly" Skelton's Quake-Tools - command-line tools for most Quake formats