Kevin Kelm's Mecha costume.
http://triggur.org/costume/mech

The web page for this nine-foot wolf robot includes well-written construction notes.

More of Kevin's costumes, including one with a carbon-fiber helmet and electronic circuit schematics at his costume site:
http://triggur.org/costume

Functional Iphone Costumes
John Savio and Reko Rivera's functional iphone costumes.

http://forums.macrumors.com/showthread.php?t=808676

Big Daddy from BioShock video game
http://volpinprops.blogspot.com/2009/09/big-daddy-bioshock.html

This monster is the incredible work of Harrison Krix, a propmaker out of Atlanta. Excellent write up of his construction techniques. He doesn't do anything half-assed.

He has many other builds on his site, each more incredible than the last.

http://volpinprops.blogspot.com/2009/10/daft-punk-helmet-part-2.html

Lord of the Rings: Sauron
http://www.flickr.com/photos/9639428@N03/3905235010/

Speeder Bike and rider
http://www.studiocreations.com/howto/speederbike/index.html

A very cool illusion beautifully rendered.

Centaur
Laecee R.

http://www.coolest-homemade-costumes.com/coolest-centaur-costume.html

This article was nearly re-titled "Awesome costumes for MEN", but lo! There are women who make supersized costumes too.

AT-AT costume
Matt and Christi

From Dragoncon 2009

2-man AT-AT costume
Jason

I believe this was in New York City.

AT-ST costume
Cheston Botso
http://my350z.com/forum/the-lounge-off-topic/391776-my-halloween-costume-2008-star-wars-at-st.html

Cheston's got a number of pretty good build logs on his site.

Ring Wraith with Hobbit in a cage
Earl Bergquist

http://www.boneboy.com/costume/02hbcg.html

This is probably the only actually scary costume in this bunch.

Alpha Flight Sasquatch
Allen Hansard and Beau Brown

http://www.thesuperherocostumingforum.com/topic/890/t/Sasquatch.html

Iron Giant Costume

This stilted giant won the top prize at the Industrial Light and Magic halloween party in 1998.

Power Loader
Ben Hallert

http://hallert.net/powerloader/

Ben is the only person I've read who cuts down on PVC because it is "too heavy". He has also built a APC (from the Matrix movies) costume and a Mech costume.

http://hallert.net

Dr. Octopus
Rob Cockerham

Build log (5 pages)

The Money you could be saving with Geico
Rob Cockerham

Build log (10 pages)

Paparazzi
Rob Cockerham

Build log (2 pages)

World of Warcraft / Diablo Costumes

Kel'Thuzad
Zachary Shaffer

Blizzcon 2009

Tier 8 Paladin
Andy "Guido" Kimble

Blizzcon 2009

Valeera Sanguinar
Jo-Jo Chen

Blizzcon 2009

Mother Shahraz
Christina Estrada

Blizzcon 2009

Draenei Shaman in Skyshatter Regalia
Brian Morris

Blizzcon 2009

Mistress of Pain
Lorraine Torres

Blizzcon 2009 http://www.alltern8.com/library/cosplay_memorabilia/article/interview

Iron Man
Russell Walks

http://s453.photobucket.com/albums/qq253/russellsculpts/Art%20of%20RussellSculpts/?action=view¤t=flip-finish4.jpg

Lord of the Rings: Helm of the Witchking

http://mydumbprojects.blogspot.com/2009_11_08_archive.html

from "Blind Squirrel" out of Arizona.
Great build log of this and many other projects. Builds real-life replicas of swords from video games and anime.

Hole Through
Evan Booth

http://www.flickr.com/photos/evanbooth/291214973/

Death Becomes Her (inspired by the "Hole Through" costume)
Nicole Magne

http://www.nicolemagne.com/blog/category/costumes/death-becomes-her-costume/

Great build logs on her site, with video.

http://www.nicolemagne.com/blog

Girl with Hair Ribbon (Roy Lichtenstein Painting)
makeup designed by Karin Stone

From a MAC makeup halloween exhibition

http://www.youtube.com/watch?v=dgmgyRX9Zn4
http://www.comicsalliance.com/2009/10/28/best-comic-book-halloween-costume/