Apple used to offer huge savings to students a few years back. I bought my first Macbook Pro with the student discount of $200 and a free $100 printer (that I sold unopened to $95), so a a svaing of $300 on a $1600 Macbook Pro in 2007. But gradually this reduced and recently it has been only around $100 (or more for higher end models) and another $100 iTunes/App store gift card. Now this is not much of an incentive like before, but still something. Also interesting is the that iPhones and iPads are now included in this student offer.
However bear in mind that the trend with Apple products has changed dramatically in the last few years. Previously you cannot get discounts on Apple products anywhere, so student discounts were very attractive, but with the proliferation of the iOS devices and the 'halo' effect, more third-party retailers have entered the business and are offering much more attractive discounts than Apple. So before any Apple purchase make sure you do your due research on the best available price for that product. Appleinsider is a good place to start.
NOTE: A valid student ID card is sufficient most of the times to avail this discount at the Apple stores or login through the Apple Education store or your school's computer store for online purchases.