Looking handsome after his first molt. This was shortly after adoption, probably sometime in late 2004.
NOOOOOOO!  September 6, 2005.  The feather that started it all.
Over the years, the area that he plucks has expanded.  This picture is from April 2009.
April 2009
He also overpreens and chews on his feathers, resulting in this ragged look.  Shabby chic!
4/23/09.  Showing off his custom-made T-shirt.  We've tried the sock buddy in the past, but it made both of us miserable.  Also, it was difficult to get the sock to cover the area on his neck where he plucks.  I decided to take matters into my own hands and hit up Jo-Anne's for some fabric.  I found a tight cotton knit that wouldn't fray and got to work.  Ulrich's been wearing his shirt for 2 days and he almost doesn't know it's there! 
The fabric only stretches in one direction, so you need to lay it out with the stretch going horizontally so you can get it over the bird.  I cut a 7" long x 4" wide rectangle and stitched along the back, tapering in at the neck for a turtleneck design. If you don't have a sewing machine, you can easily do this by hand.
You'll want to cut the bottom front shorter so the bird doesn't poop on his new shirt. Then cut the slits which you will pull both the wings and the feet through.  The slits should be crescent shaped. Unfinished edges won't fray if you select a good fabric.  Voila!  Don't turn it inside out.  The exposed stitching goes along the back.  
I included the pictures and directions for making the shirt to show that it's not that difficult to make a custom shirt for your bird.   Bear in mind that this particular one is tailored specifically for Ulrich (comes up high on his neck), so if you decide to make your own, you will have to alter it a bit.  But give it a try.  It's so much better than a sock!
July 2009, after wearing shirts for 10 weeks
April 2009
***BUY A SHIRT!*** I've had many people ask me if I was selling these shirts.  They are really easy to make and I recommend you try it yourself since you know your bird and the particular plucking issues.  However, if you would rather purchase one, I will make one for your bird for $10.  See this page for more info.
Video of Ulrich wearing his shirt