This is a huge list that Xooxer dug up from the Pixelation forum.

Pixel Tutorials
Isometric Tutorials
Zoggles - http://www.zoggles.co.uk/asp/tutorials.asp?show=index
Pixelfreak - http://www.pixelfreak.com/en/tutorial0.html
Pixel NascImpact - http://pixel.nascimpact.com/tutoriaux.php

General Pixel Art Tutorials
Gas13 - http://gas13.ru/tutorials/
AbsoluteV3 (AA) - http://neota.castleparadox.com/aa_tutorial.html
Matriax - http://www.matriaxweb.com/tutoriales/tuto.htm
Drububu - http://www.drububu.com/tutorial/index.html
Natomic - http://www.natomic.com/hosted/marks/mpat/

General Art Technique
http://www.itchstudios.com/psg/art_tut.htm

Backgrounds
http://www.barnettcollege.com/tutorial1.htm
http://allitis.com/agast/backgroundex1.html

Colouring
http://elfwood.lysator.liu.se/farp/colorps/pcolorps.html

Light
http://www.itchy-animation.co.uk/light.htm

Anatomy
http://www.figuredrawings.com/linksanatomy.html

Animation Tutorials and Reference
Eadweard Muybridge - http://www.brianlemay.com/animationexamples/ animationindex.html
http://www.idleworm.com/how/index.shtml
Don Bluth - http://www.donbluth.com/academy.html
http://www.awn.com/tooninstitute/lessonplan/lesson.htm#top