Nice find! ISIC (International Student Identity Card) is a student ID card for full-time students that provides discounts for students all over the world. When I was a student at Georgia Tech, they had an office on campus that processed applications. I remember the ISIC card being particularly useful in Europe, as many places only gave student discounts with an ISIC card.
I think it cost around $30 (annually), but that may have changed since the last time I got one (2001). I definitely made up the cost of the card with the discounts I got, but it was much more useful outside the US; many places in the US will give you a student discount with your regular school ID. For anyone who is interested in the card, check out the website for more info:
www.isic.org.