Everyone has provided a great list.
I just wanted to reiterate that once you can book activities, you will be able to see your choices (excursions, spa, Palo/Remy and events) for each day to make it a little easier to plan. Registrations for children's programs are done during Online Check In. I find the website generally very easy to navigate. Just pay close attention to cancellation deadlines for these:
For Port Adventures: reservations must be canceled at least 3 days prior to the cruise departure date. After that time all reservations are final and non-refundable.
For Spa & Salon facilities: appointments must be canceled 24 hours in advance to avoid a 50% cancellation charge.
For Babysitting: reservations must be canceled at least 4 hours in advance to avoid a 50% cancellation charge. Guests who fail to arrive for a reservation without canceling will be charged the full cost of the time reserved.