Resources I find useful.

Gaia Threads

The Color Scheme Guide Compilation Thread by Zeetheus
The New Color Scheme Guide Compilation Thread by emetology

Taking the Scenic Route: A Scenic Guide & Catalog by Khenarthi
Lighting Mod List by hiimbeary
Background Cutter Items by Aerdian
Avatar Tricks: Foreground Cutting by Aerdian

Make-up & Facial/Muscle/Bust Definition by ElegantlyLuminous
scissors + misc mods list (clothes, haircuts) by emetology
Bewere/Cheshire/SurgicalScissors Cutter Mod Item Guide by Aerdian
The Ultimate Hair Guide by LayDeDeadpool

How to Make a Good Avi - Some Observations by 0ri0

Challenge Resource/Inspiration Thread
The Every Evolving Item Challenge - by Katolincat