Popular JavaScript pattern, var Module = (function() { ... })();
Module pattern helps to avoid namespace conflicts, and thus is widely use by various third-party scripts, like libraries or banners.
Major drawbacks of using it are: much more difficult debugging and low IDE support.
var Module = (function ( ) {
...
})();
Original presentation at YUI blog. More detailed explanation by Ben Cherry.
Critique: by Jonathan Snook and Ed Spencer