I would like to see some public-facing sites or complex business applications built on top of SHarepoint 2010 (or at least 2007). They can either use Sharepoint's look'n'feel or have a completely custom one.
If they're using Silverlight in heavy doses even better.
Try http://www.topsharepoint.com/ - they supposedly keep a list of the best SP sites they have come across.
Also MS site has case studies - there are a lot of "internal" ones described so no example or site but some of them have links. http://sharepoint.microsoft.com/en-us/customers/Pages/default.aspx?Edition=SharePoint%202010
(That is only the 2010 page but you can get to the 2007 ones as well).
Check academic site, it's made with Sharepoint 2007. Their application system, and career portal also runs on Sharepoint as well as the their academic intranet, which creates course sites with student forums, asignments etc. using enrollment data from their CRM.