For awhile now, I've been looking for PSD Thumbnail support in explorer. I recently stumbled across SageThumbs, which is completely free and works with Windows XP/2003/Vista/2008/7 32/64-bit. Plus it's open source, which is pretty neat.
SageThumbs on Google Code (http://code.google.com/p/sagethumbs/)
Quote from: FeaturesExtended thumbnail image view of Explorer folder
Thumbnail image in explorer context menu (right-click menu)
Extended info tips
Support 162 image formats (224 extensions) via GFL Library (http://xnview.com/en/gfl.html)
Support additional 26 image formats via XnView plugins (if installed)
Send by mail support
One-click conversion to popular image formats support
Wallpaper selection support
Copy to clipboard support
Here's a screenshot I took.
(http://i.imgur.com/8Vlz5.png)