I started putting together Layered PSD files of starter themes styleguide,using the styleguide module http://drupal.org/project/styleguide.
EDIT: All the PSD styleguides are now available on Github https://github.com/waako/Drupal-Themes-Styleguide/ each theme has it's own branch
I have done one, or several, for the following base themes:
Omega Alpha subtheme (includes the Omega theme development blocks and grid) (http://drupal.org/project/omega):
http://dl.dropbox.com/u/124467/drupal/design/omega-alpha_blocks-grid.psd...
Framework (http://drupal.org/project/framework):
http://dl.dropbox.com/u/124467/drupal/design/framework.psd.zip
Hex Starter (http://drupal.org/project/hexagon):
http://dl.dropbox.com/u/124467/drupal/design/hex-starter.psd.zip
Ninesixty (http://drupal.org/project/ninesixty):
http://dl.dropbox.com/u/124467/drupal/design/ninesixty.psd.zip
Zen (http://drupal.org/project/zen):
http://dl.dropbox.com/u/124467/drupal/design/zen.psd.zip
Genesis (http://drupal.org/project/genesis):
http://dl.dropbox.com/u/124467/drupal/design/genesis.psd.zip
Stark (http://drupal.org/project/stark):
http://dl.dropbox.com/u/124467/drupal/design/stark.psd.zip
Basic (http://drupal.org/project/basic):
http://dl.dropbox.com/u/124467/drupal/design/basic.psd.zip
Adaptive Theme (http://drupal.org/project/adaptivetheme):
http://dl.dropbox.com/u/124467/drupal/design/adaptivetheme-starter.psd.zip
Fusion (http://drupal.org/project/fusion):
http://dl.dropbox.com/u/124467/drupal/design/fusion-starter.psd.zip
Clean (http://drupal.org/project/clean):
http://dl.dropbox.com/u/124467/drupal/design/clean.psd.zip
Squaregrid (http://drupal.org/project/squaregrid):
http://dl.dropbox.com/u/124467/drupal/design/squaregrid.psd.zip
Tao (http://drupal.org/project/tao):
http://dl.dropbox.com/u/124467/drupal/design/tao.psd.zip
These PSDs are not organised, they are just everything in the page layered.
I was going to maybe use a PSD cleaning service, but both sites I had bookmarked don't exist anymore (psdcleanup.com and tidypsd.com).
So I can create a PSD or PNG styleguide for any theme, and try and do a basic layer organisation, but it would be up to you to organise it for the designer.
Having one of these to hand to a designer who is not familiar with Drupal seems to be very helpful, as it would help familiarise them with default elements and speed up work for the themer.
What elements do people think are important to include in the file?
I approached having multiple pages, a styleguide page, login/register/resend, homepage with generated content from devel module and navigation.
EDIT: changed urls to zipped versions

Comments
Wow - this is amazing
Wow - this is amazing work!
I'm not sure yet - but I think I'm trying to do something similar in a sandbox SVG UI Widgets project...
http://drupal.org/sandbox/kattekrab/1263304
Donna Benjamin
Former Board Member Drupal Association (2012-2018)
@kattekrab
Can you zip these files?
for example, tao.psd = 64mb, zipped it is 2.5mb
Good point, I'll zip them
Good point, I'll zip them up.
Also, I'll create a GitHub repo with everything
Thank you
Wow!!
Thank you very much for your contribution to the community waako!
Github Repository
I have pushed everything to Github repository https://github.com/waako/Drupal-Themes-Styleguide/
There is a seperate branch for each Theme, including a jpg preview of the PSD files.
I do feel that the styleguide module could do with some extending, some HTML content elements and maybe include some more form elements like the login page etc, then we would end up with something more like http://www.chapterthree.com/greyboxing
Awesome :)
It's like being at the top of the Faraway tree when the land of goodies is there.
Zen? Neh, too heavy on the stomach ... Oooh Tao!
waako++ will you accept .xcf
waako++ will you accept .xcf versions for those on gimp? (psd to xcf doesn't always work as expected wrt layer styles).
@larowlan I have no idea how
@larowlan I have no idea how to create a layered .xcf but if you can, then please, add them to github repo :)