Online Tutorials:
Beginner: for complete beginners.
Sashas penciling tutorial
Great introduction to pencil drawing.
Intermediate: for those who have some mastery of the basics.
Wacom: Photoshop+Painter
Shows some of the more advanced brush settings.
Snarly tutorial
How to draw snarly wolves, if you ever come to draw snarly wolves. XD
Sashas tutorial collection
Plenty of help for pencil drawing. Beginner-intermediate material.
CGSociety's articles: tutorial section
Intermediate-advanced material. I'd look at the earlier articles, the most recent ones are mostly walkthroughs.
Philip Straub - CGSociety - composition tutorial
One of the neatest guides about composition I've seen around.
Advanced: for those who know their stuff.
Painting via Adjustment Layers
Good technique to try out.
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Books:
ConceptArt's Art E-book collection
Download your heart out.
Complete Loomis
Loomis is awesomesauce. Get them.
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Misc. Resources
The Grimace Project
References for those who want to add some emotion to their characters.
Posemaniacs
Human construction references.
TypeWorshop
Offers the basics of typography design.
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Artists
1xSemana sketchblog
Many artists post on this place, a variety of art styles. Unfortunately, no longer active.
Matthew Woodson
I like his style, vector cleanness.
dump of paint
Amazing sketchbook.
Thomas Canty
Ryohei Hase
Rey Bustos
Full of art, resources. I find his anatomy sketches particularly helpful.
Harry Clarke
A personal favorite.
Jean-Luc Grondin
Robert Bateman
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Art Websites
3DTotal
CGSociety
ConceptArt
