Using JQuery, takes any link in the login form of a particular class, automatically converts the text to an ID-able string (e.g. "Phone Number" -> "session_phone_number"), and then shows that div and hides all the others.

swapping_login_methods.js

$(document).ready(function()	{
	$('#LoginForm a.login_method_switch').click(function()	{
		var blockToShow = '#session_' + this.text.toLowerCase().replace(' ', '_');
		$('#LoginForm ' + blockToShow).show("slow");
		$('#LoginForm .session_login_method:not(' + blockToShow + ')').hide("slow");
	});
});