QuakeOne
Quakeone.com
Inside3D
Forums.inside3d.com
Func_Messageboard
Celephais.net
Quaddicted (includes download mirror)
Quaddicted.com
I should also mention I didn't make this on my own! Co-authors were MFX and Hrimfaxi, both seasoned mappers. And we had a load of engine and playtesting support from various modders - the readme and credits map detail their contributions.