Quake Info Pool …all about Classic Quake of id Software by Maddes…
Linux Quake How-To
Quaddicted.com browse and download all known and preserved Quake Singleplayer Maps
Slipgate Construct
Kawaiik - Quake 1 redesign project
QuakeOne
QuakeOne Navigator links to other Quake sites.
Quaketastic Quake related downloads.
Quake Wiki
The Gamer's Guide - GL Quake
aRQ-Lite
DarkPlaces
DirectQ (GitHub)
Engine X
ezQuake
Fitzquake, SDL version, Fitzquake Mark V
Fodquake
FTE QuakeWorld adds some cool features to QuakeWorld, without loosing any (backwards) compatibility.
FuhQuake for MacOS X
JoeQuake
Non-PhotoRealistic Quake met sketchy, blueprint en brushstroke renderers.
ProQuake 4 is the official continuation of the original ProQuake by J.P. Grossman.
Q2K4
QMB, GitHub - DrLabman/QMB
Qrack
Quake Royale
QuakeForge
Quakespasm, GitHub - ericwa/Quakespasm
Quore is an atmospheric Quake engine running on GNU/Linux systems with enhanced graphics, increased limits, configurable HUD and ambiences, and different modes for changing the gameplay. It is based on JoeQuake with additional effects from Qrack, ezQuake and engine's limits tweaking from Fitzquake.
QuDos Linux Quake binaries, see GitHub - ZwS/qudos
Telejano
TomazQuake
Tremor (dead link)
TyrQuake
ZQuake, GitHub - ZQuake
cy6erGn0m's page Quake 1 for Linux with fixed sound output. (Also links to meqcc and fqcc, fastqcc.)
Quake on an oscilloscope: A technical report
GitHub - Novum/vkQuake Quake port based on QuakeSpasm for the Vulkan graphics API.
GitHub - sultim-t/vkquake-rt vkQuake Ray Traced.
Quakespasm-Spiked (aka: QSS), GitHub - Shpoike/Quakespasm.
Good Looking Quake is a very conservative source port of Quake. It is designed for those who grew up playing the original DOS Quake and wish to preserve that specific look and feel, as much as possible. By atsb.
JLQuake is a Quake engine source port with support for Quake, Hexen 2, Quake 2, Quake 3 Arena, Return to Castle Wolfenstein and Wolfenstein: Enemy Territory. Main goal is to create a common rendering engine for all of these games and extend it further. (sourcecode only)
Quake Wiki - Engines (dead link)
QCide & Clean QuakeC offers an IDE for QuakeC and cleaned up QuakeC sources for Quake and QuakeWorld.
the homepage of Bengt Jardrup
Fabien Sanglard's non-blog - Quake Engine code review
Dead links:
Quake Injector is a (Java based) tool to download, install and play Quake (some call it „Quake 1“) singleplayer maps from Spirit's Quaddicted archive
GitHub - gmqcc An Improved Quake C Compiler
QCide
MultiPlayer Quake Archive
John Fitzgibbons maps for Quake I and II.
Improved Quake
Vengeance r2
Travail
Quoth
Feral and Feral Flesh
ReMakeQuake is a mod (partial conversion) project offering a fresh perspective on the ’90s cult shooter game, QUAKE. (discontinued).
Rune Quake
SimonOc - In The Shadows features a new gameplay mode called Stealth, several highly detailed maps and loads of new visual updates. ModDB - In The Shadows