laravel/app/Http/Filters/GuestFilter.php

<?php namespace App\Http\Filters;

use Auth, Redirect;

class GuestFilter {

	/**
	 * Run the request filter.
	 *
	 * @return mixed
	 */
	public function filter()
	{
		if (Auth::check())
		{
			return Redirect::to('/');
		}
	}

}