In Spain hostel cards and student / youth cards can save you money on travel (bus, train and domestic air fares), accomodation and museum entry. A European passport if you are under 25 years or over 65 years can also be used for discounts.

STUDENT AND YOUTH CARDS
Student cards from your own country are worth bringing with you, however you may also need an internationally recognised card like the ISIC (International Student Identity Card) or ISE (International Student Exchange Cards). If you are not a student but under 26 years you can qualify for a youth discount card. The ISE card costs US $25 and can be ordered online at http://www.isecards.com

ISIC has three discount cards for teachers, students and travellers aged under 26. The ISIC card is the most widely accepted and many travellers pick up fake versions in Asia. Because of this you may be asked for a secondary identification such as your student university card. The IYTC card is an alternative if you are under 26 and the ITIC card is for full time teachers. These two cards are good if you don't qualify for anything else.

HOSTEL CARDS

Hostels of Europe, VIP and YHA (Hostelling International) all offer excellent discounts particularly for transport and accommodation. It may be worth getting more than one card. Hostels of Europe provides discounts in hostels in Italy and around Europe. You can order it online. The VIP card gives discounts of around 5%. Hostelling International cards can be bought at the hostel premises but may cost more than at Hostelling international offices. They cost approximately US $25 but it does vary from country to country but you can earn points towards a membership if you stay at a hostel at the non-member rate. The card also includes transport discounts for car rental, bus and train travel.