2 sites from me in private beta:

http://www.iddaamacsonuclar.com Interactive Web App Directory meets Newsreader.

http://www.quartzbeautyclub.com Social Shopping.

Beta users welcome. Just sign up directly or send me an email (arda [at] gmail [dot] com).

http://www.mirko-franz.de
http://www.skiwiese-bad-nauheim.de

Both are using PIE for rounded corners and box-shadows.

Using PIE for border-radius and box-shadow at So We are Dads. Not used for the gradient in the search drop down though. Works fantastically from IE6 thru 9 and when text-shadow gets added my site will finally look the same for all tested browsers.
Thank you for your work, it really does work wonderfully.

Here are 3 of my sites using PIE

1)
Static site with pure pie-css3 power: Imagine - no decoration images were used - its only css and pie. The only images on this site are the pictures take by a camera.

http://www.goodlack.at

2) A Joomla 1.7 installation with SEBLOD and PIE working together

http://www.hausbau-ratgeber.at

3 A Joomla 2.5 installation in HTML5, K2 and PIE (this site is under construction at the moment, but you can see the effects)

http://www.enjoy-living.at

Best regards Jürgen

Using a lot at:
http://web-bookcase.ru/ - webmasters stuff in Russian

and

http://www.searates.com/ - world shipping community