Was looking for some song lyrics today and the first Google hit was to:
Notice the .nsf in the path? I saw the UNID and thought it looked Notes-ish. So then I looked on to the left and saw the nsf.
According to Netcraft, it's running Domino 5.0.9 on Linux. It's a pretty quick site though - imagine it on 6.5 or even 7 with the Linux improvements 7 will have!