Microsoft has (or had) a project. I think this is ugly and completely misses the charm of a clock.
http://research.microsoft.com/en-us/groups/sds/whereabouts_clock.aspx
John McKerrell has a nice build using an arduino and mapme.at
http://blog.johnmckerrell.com/2009/06/01/hacking-location-into-hardware/
University of Munich Team Effort
http://www.alastairbarber.com/index.php?post=harry-potter-weasley-clock