Yes! Either of you can start the list and add the other. To do this, have your list open that you wish to collaborate on. Select the settings icon next to the top dropdown box. This will open the setting page. Look for the Collaborate box, fill in the other's email address and click "add". Now it should show them listed below the green bar. Here you can give permissions or even remove them if they are really bad. This is perfect for Holiday gift giving items too by the way.