$.NameOfClass is an alternative way to name a plugin function name. The other way is $.fn.NameOfClass. Both are frequently done together because they offer slightly different functionality, mostly because of the scope they expose themselves in.
$('#foo .bar').doStuff(); // do something to a DOM element
var stuff = $.doStuff(); // do something without a DOM element as context
Sometimes the function doesn't have to operate on a DOM element but can do other things, like make measurements. In this case the $.NameOfClass way is useful. Some native jQuery functions work like this, e.g. most of the ajax stuff.
See this article for a better example.