NS, the Dutch railway company, is currently offering train travellers a 50 percent discount on the price of an annual subscription to their off-peak travel discount card. A subscription normally costs 50 euros per year, but those who sign up through October 15 can pay just 25 euros for their first year.
The voordeelurenabonnement card gives users a 40 percent discount on travel during off-peak hours (before 6.30am, from 9am - 4pm, and after 6.30pm) and on the weekend. If you're travelling with friends, up to 3 of them can also get a 40 percent discount on their tickets after 9am and on the weekend.
A subscription includes a personal OV-chipkaart (normal price is 7,50 euros), which you can top up at ticket machines in train stations. The subscription is continuous, and once your first year is over it will cost 50 euros to renew it (although you can end your subscription on a monthly basis if desired).
Note that purchasing the card via their webshop will not be possible on October 13 because the website will be under maintenance. You can alternatively place an order over the phone by calling their customer service line at 09002021163 (costs 10 cents per minute, available Mon-Fri 8am-10pm and Saturday 9am-5pm).