For travelers planning day-trips that include trains and other forms of public transportation, there is now a great deal from NS:
off-peak Holland Day Travel Ticket - € 39
It is valid on all forms of domestic public transportation, any day, any time except Monday-Friday 6:30-9 AM
The price includes the disposable OV-Chipkaart. It is sold only on NS costumer desk or NS ticket machines and nowhere else.
For people staying in Amsterdam, this option will be cost-effective for day-trip destinations like Delft, Arnhem, Rotterdam, Giethoorn, Den Bosch, Maastricht, Nijmegen etc.