I searched and saw a couple passing references to this, but after suggesting it to cadets last week, I thought it was worth bringing up to members who might not be aware of it:
Eastern Mountain Sports offers a 15% discount (and 20% off their own brand) for students with a valid student ID. All you have to do is take your ID, and they give you a discount sticker.
I've bought a lot of great gear for outdoor activities and CAP ES from EMS. Smartwool is one of my favorite product lines there - GREAT socks, glove liners, thermal undergarments, and such. You can also get a discount on some brands that are often excluded from sales or discounts - like The North Face.
They also have good water purification products, food products, compasses, GPS units, etc., etc. etc. I got a SteriPEN Water Purification at an amazing price a while back.
Details here:
http://www.ems.com/helpdesk/index.jsp?display=promos&subdisplay=student (http://www.ems.com/helpdesk/index.jsp?display=promos&subdisplay=student)
Really great and reliable products.
They actually outfit the folks up on Mount Washington, NH, for free. In return, their products are getting tested in some of the worst weather on Earth.