One of the greatest features of Spotify is the ability to share music with your social graph. With a few lines of code, we can interact with the "Share" popup dialog.
/* Instantiate the global sp object; include models */
var sp = getSpotifyApi(1);
var models = sp.require("sp://import/scripts/api/models");
/* The div that will contain the popup */
var element = $('#share');
/* The Spotify URI of the content you want to share */
var content = 'spotify:track:76a6mUM5r7VPexAj37TLjo';
/* Display the popup */
models.application.showSharePopup(element[0], content);