When can I travel again after childbirth?

Depends. You should be able to travel as soon as you want and are able after your delivery. For many women travel is ok within a couple weeks afte delivery.
Travel with caution. You get get back to travel when you feel comfortable going on the trip. Get plenty of rest around your trip and keep yourself healthy. Take the same travel precautions you have in the past and keep in mind the newness of travel with a newborn. Extra clothing, food, diapers, and a treat for yourself. Optional earplugs for your fellow passengers can be a nice touch.