Direct quote from John Nack’s blog:
“Extract, Pattern Maker, Web Photo Gallery, Contact Sheet, Picture Package, and PDF Presentation have been removed from the default installation.  The latter four have been replaced by the Output module in Bridge CS4, and our intention is to replace Extract with features inside Photoshop (building on Refine Edge & more).  All of these except PDF Presentation will remain available as optional installs (to be posted on, but over time they’ll be phased out. “