We've seen the W+K ones from London and Amsterdam... here are a few from Australia. The first is from Host Sydney and is based around a Christmas tree that you post tweets on as decorations. The second is from The Jamboree and is a bit out there as it's all about Christmas 'Carols'. The third is from Euro Sydney that is based on the Angry Birds app, but using staff faces as the birds. Check 'em out.
Hosts Christmas Message is kinda cool - bit like W+K London's one
From The Jamboree - only about 8 Carols (bugger)
Euro's Angry Birds effort - cool