Most of the links are for Q3, but the Radiant editor us fairly the same for every game, just minor differences.
I'll keep updating the list. (got most of this from: http://ugg.codealliance.ca/tutorials )
Tutorial Sites
Quake 3:
http://planetquake.com/qworkshop3/tutorials/
http://quake3.qeradiant.com/tutorials.shtml
http://planetquake.com/bubba/
http://www.planetquake.com/gothic/
http://www.greeneggsnspam.com/tutorials.asp
http://fnf.20m.com/tutorials.html
http://mappers.uffiles.com/
http://www.nibsworld.com/rtcw/
http://www.planetquake.com/q3empire/
http://www.planetwolfenstein.com/wump/
JK2 :
http://richdiesal.jedioutcastmaps.com/main/index.html
Curves
http://planetquake.com/qworkshop3/tutorials/corners/index.html
http://quake3.qeradiant.com/curves/curvemenu.shtml
http://quake3.qeradiant.com/q3afiles/curves.htm
http://www.planetquake.com/gothic/tutorials/bevel.html
http://www.planetquake.com/gothic/tutorials/invertbevel.html
http://www.greeneggsnspam.com/tuts/map4/index.asp
http://www.planetquake.com/q3empire/data/tutorials/q3r/basics_curves/curves.htm
Doors
http://www.planetquake.com/gothic/tutorials/door.html
http://planetquake.com/bubba/door1.html
http://planetquake.com/bubba/butt1.html
http://www.planetquake.com/gothic/tutorials/door.html
http://fnf.20m.com/q3rtut4.html
http://www.nibsworld.com/rtcw/tutorial_rotating_door.shtml
http://www.planetquake.com/q3empire/data/tutorials/q3r/basics_doors/door.htm
http://www.planetwolfenstein.com/surface/tutorials/sliding_doors.html
http://www.planetwolfenstein.com/surface/tutorials/rotating_door.html
First Room
http://planetquake.com/qworkshop3/tutorials/firstroom/
http://quake3.qeradiant.com/q3afiles/creatroom.htm
http://planetquake.com/bubba/room.html
http://www.planetquake.com/gothic/tutorials/createroom_1.html
http://www.greeneggsnspam.com/tuts/map1/index.asp
http://fnf.20m.com/q3rtut1.html
http://www.nibsworld.com/rtcw/tutorial_second_room.shtml
http://www.planetquake.com/q3empire/data/tutorials/q3r/basics/basics.htm
http://www.planetwolfenstein.com/surface/tutorials/first_room.html
Fog
http://planetquake.com/qworkshop3/tutorials/fog/index.html
http://planetquake.com/qworkshop3/tutorials/hellfog/index.html
http://planetquake.com/bubba/fog1.html
http://www.planetwolfenstein.com/surface/tutorials/fog.html
Glass
http://planetquake.com/qworkshop3/tutorials/glass/index.html
Grates
http://planetquake.com/qworkshop3/tutorials/grates/index.html
http://quake3.qeradiant.com/q3afiles/shader02.htm
Hallways
http://planetquake.com/bubba/connect.html
http://www.greeneggsnspam.com/tuts/map2/index.asp
http://www.nibsworld.com/rtcw/tutorial_second_room.shtml
http://www.nibsworld.com/rtcw/tutorial_connecting_rooms_advanced.shtml
http://www.planetquake.com/q3empire/data/tutorials/q3r/basics2/basics2.htm
Lighting
http://planetquake.com/qworkshop3/tutorials/light-help/index.html
http://planetquake.com/qworkshop3/tutorials/light_effect/index.html
http://planetquake.com/bubba/beam1.html
http://www.planetquake.com/gothic/tutorials/lighting_1.html
http://www.greeneggsnspam.com/tuts/map9/index.html
http://fnf.20m.com/glight.html
http://www.planetquake.com/q3empire/data/tutorials/q3r/basics_light/light.htm
http://www.planetwolfenstein.com/surface/tutorials/using_lights.html
http://www.planetwolfenstein.com/surface/tutorials/spotlights.html
Liquids
http://planetquake.com/qworkshop3/tutorials/water/index.html
http://quake3.qeradiant.com/q3afiles/water1.htm
http://planetquake.com/bubba/liquid1.html
http://www.planetwolfenstein.com/surface/tutorials/water.html
Radiant Setup
http://planetquake.com/qworkshop3/tutorials/q3rbasic/index.html
http://planetquake.com/qworkshop3/tutorials/bspmenu/index.html
http://quake3.qeradiant.com/q3afiles/overview.htm
http://quake3.qeradiant.com/q3afiles/gtk01.htm
http://quake3.qeradiant.com/efradiant/efrad01.htm
http://planetquake.com/bubba/intro.html
http://planetquake.com/bubba/compile1.html
http://www.planetwolfenstein.com/surface/tutorials/getting_started.html
Sky
http://www.nibsworld.com/rtcw/tutorial_skybox.shtml
http://www.planetwolfenstein.com/surface/tutorials/making_sky.html
Sounds
http://planetquake.com/qworkshop3/tutorials/speaker/index.html
http://planetquake.com/qworkshop3/tutorials/music/index.html
http://planetquake.com/bubba/sound.html
http://www.planetquake.com/q3empire/data/tutorials/q3r/music.htm
http://www.planetwolfenstein.com/surface/tutorials/using_sounds.html
Stairs
http://planetquake.com/qworkshop3/tutorials/stairs/index.html
http://planetquake.com/bubba/stairs1.html
Textures
http://planetquake.com/qworkshop3/tutorials/texture-align/index.html
http://quake3.qeradiant.com/q3afiles/shader01.htm
http://www.planetquake.com/q3empire/data/tutorials/q3r/basics3/basics3.htm
Troubleshooting
http://planetquake.com/qworkshop3/tutorials/leak/index.html
http://planetquake.com/qworkshop3/tutorials/sparkles/index.html
http://quake3.qeradiant.com/q3afiles/leaks.htm
http://quake3.qeradiant.com/q3afiles/condump.htm
http://quake3.qeradiant.com/q3afiles/gtk04.htm
http://quake3.qeradiant.com/errors.shtml
http://www.planetwolfenstein.com/surface/tutorials/sparklies.html





