Making a list of sites blocked in office because of Websense (or Webnonsense as @prolificd puts it ) here’s an incomplete list so far. Have a look at FriendFeed’s classification!
Access to this URL is currently restricted due to a blocking rule.
URL: http://webcast.cern.ch/ Rule: Block URLs of type Education
URL: http://friendfeed.com/ Rule: Block URLs of type Personals/Dating
URL: http://labnol.org/ Rule: Block URLs of type Business/Economy
URL: http://twitter.com/home Rule: Block URLs of type Social Networking
URL: http://www.facebook.com/ Rule: Block URLs of type Social Networking URL: http://docs.google.com/ Rule: Block URLs of type Personal Network Storage/File Download Servers
URL: http://imdb.com/ Rule: Block URLs of type Arts/Entertainment
URL: http://digg.com/ Rule: Block URLs of type Arts/Entertainment