Wrote a short blog post on some of the best SilverStripe cases I've been able to find around the globe:
http://www.floapps.com/silverstripe-creme-de-la-creme/
Currently the list at
http://www.silverstripe.org/who-uses-silverstripe-cms/
is mostly sites from NZ / Australia region and would love to see more variety there. A good list of best showcases helps us SilverStripers to convince potential clients better.
Btw, on the front-page of silverstripe.org it still says "Over 2,500 sites in our community showcase" while the number is already above 3,000.