The standard edition of Guild Wars 2 is normally priced at $59.99, but with this promotion, you can pick it up for $47.99. To get the discount, you'll need to pre-order it through Newegg.com (obviously) and use the following promotion code: EMCYTZT1867.
It's important to note that this is a retail box copy that will ship on release, not the digital download. Also, this promotion applies to today (July 7th) and today alone.
[Thanks to Nitai for the tip!]