LEVEL DESIGN:
Bubba's Arena Mapping Bubba's Arena Mapping (mirror)
Mapping 4 Newbies
SimonOC Articles
RTCW/ET Mapping Tutorials - all apply to Quake3 mapping
Q3 ASE Shader Editor
Cardigan's Mapping Tips
GtkRadiant Wikibook
Online Q3 Shader Mnaual
RESOURCES:
Surface Mapping Resources
Rich Diesal's JK2 mapping guid
EASYGEN:
EasyGen Website
ReD NeCKersoN's Video Tutorial Series
TramDesign Easygen Tutorial
Modsonline Easygen Tutorial
OPTIMIZATION:
Advanced Portal and Hinting Optimization Tutorial
Nib's Detail & Hint Brushes Tutorial
Cardigan's Bot Optimization Tutorial