Included in the list of innovations found in the Family.Show genealogy sample application is the surname cloud. Similar to the tag cloud that you find in many web application today (Flickr, LibraryThing, Technorati, etc.), the surname cloud lists the last names of all people in your database. This surname cloud lists names alphabetically with those surnames appearing more frequently appearing in a larger font size.
When you click on a name in the surname cloud, then the person list is filtered to only show those that have that last name.
I have yet to see a surname cloud in any other genealogy software.