Starting today (January 3rd) php architect are running their '7 days' promotion. For each of the following days you can buy certain products at heavily discounted rates. Today the offer is for 50% off the cost of the Zend PHP 5 Certification Guide book (both print and PDF version).

This means you can pick it up for $17 instead of $35. Of course shipping costs are added on-top of this, but they're the same as usual and it's a great way to pick up a very good book, half price. Check out the offers here: http://www.phparch.com/sevendays.