Pixel Tutorials
Isometric Tutorials
Zoggles - http://www.zoggles.co.uk/asp/tutorials.asp?show=index
Pixelfreak - http://www.pixelfreak.com/tutorial/
RhysD - http://rhysd.syntesis.org/tutorial/
http://www.webclass.ru/tut.php?tut=129
http://www.deviantart.com/view/2866522/
Pixel NascImpact - http://pixel.nascimpact.com/tutoriaux.php
http://www.decile.net/tutorials/photoshop/techniques/pixel/

General Pixel Art Tutorials
Tsugumo - http://pixeltutorial.cjb.net/ (the original!)
StOven - http://www.spriteart.com
Zoggles - http://www.zoggles.co.uk/asp/tutorials.asp?show=index
Gas13 - http://gas13.ru/tutorials/
Nemesis (AA) - http://www.rpi.edu/~laporj2/essays/aa/
AbsoluteV3 (AA) - http://neota.castleparadox.com/aa_tutorial.html
Pep and Helm (coloring/shading) - http://www.rpi.edu/~laporj2/essays/tagteam/
Blackeye Software - http://www.ocf.berkeley.edu/~derekyu/ (it's under Miscellaneous)
Matriax - http://www.speccy.org/remakesgraph/tutoriales/tuto.htm
Biomors - http://home.houston.rr.com/monkeygraphics/texturetutorial/
Biomore :P - http://home.houston.rr.com/monkeygraphics/treetutorial/
Enterbrain - http://www.enterbrain.co.jp/digifami/digiweb/dot_teck/3nen/ 3_01.html (Japanese only, but worth digging around for stuff)
PixelZone Tutorials - http://pixel-zone.rpgdx.net/shtml/tutorials.shtml
Mozco Metallic Objects - http://www.tcp-ip.or.jp/~s-iga/tips/2-3metallic_objects.html
Drububu - http://www.drububu.com/tutorial/flashtival.html (combining Flash and pixels)
Vlink.Vwalker.com - http://home.earthlink.net/~marktroup/vlinkdotvwalkerdotcom/ vlink.html
(please note that the original vlink site disappeared, this is what I salvaged from my hd)
http://koti.mbnet.fi/~aholattj/pixeltut/
Natomic - http://www.natomic.com/hosted/marks/mpat/
OurCall - http://www.ourcall.org/
http://www.pixel2life.com/tutorials/ photoshop.php?tut=4&subtut=42

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

Backgrounds
http://www.barnettcollege.com/tutorial1.htm
http://allitis.com/agast/backgroundex1.html
http://www.gfxartist.com/features/tutorials/27609

Colouring
http://elfwood.lysator.liu.se/farp/colorps/pcolorps.html
http://www.sijun.com/dhabih/mainscreen.html

Details
http://www.elverquisst.se/grasstut.html
http://www.optidigit.com/stevens/cloudtut.htm

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

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

Animation Tutorials and Reference
Eadweard Muybridge - http://web.inter.nl.net/users/anima/chronoph/first-15/ index.htm
http://www.brianlemay.com/animationexamples/ animationindex.html
Preston Blair - http://www.freetoon.com/index.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

You can also find them here: http://www.byondscape.com/ ascape.dmb?type=%2FForm%2FSearch&query=pixel+tutorials&categ ory=All+Content