I've collected some tutorials from 4chans /ic/ sticky here for easy viewing. As a professional artist I can verify every one of these links is legit and a valuable resource to improving your artistic skill.
Tutorials
NOTE: Some of these links will contain reference nudes and a while there should be nothing sexually explicit, it's technically NSFW.
Autodestruct.com
Design lectures
Anons pastebin tutorial mishmosh
Pastebin of notable tutorials focused on comics and animation.
CtrlPaint.com
Excellent resource for the beginner digital artist.
Loomis.
Loomis. Comprehensive drawing tutorials.
PSG Art Tutorial
A comprehensive set of high quality articles/tutorials regarding art technique.
Composition Tutorial by Phil Straub
Learn the basics of composition article by Phil Straub hosted on CG Society.
Guneys Journey
Valuable resource from James Gurney. Light and color focus.
Flooby Noobies Tutorial Page
Basic to Advanced Color Theory and Illustration Techniques for Photoshop
Art Books Public Domain
Artist Handbooks, Art Techniques and Painting - Free Art Books
Dueys Drawing Tutorials
Tutorials by Brian Duey.
Art wiki
Art wiki, general tutorial compilation.
Drawspace Tutorials
Learn to Draw. Over 200 free tutorials.
Drawing Tutorials Online
DrawingTutorialsOnline.com
The Art Classes
TheArtClasses.com by idrawgirls.
Fellowbros Book Collection
Drawing books including Anatomy and the Baroque drawing course.
Character Designs
General resources.
Here's an image from one of my favorite tutorials from PROMETHEUS ANJ (link included in article!)