In the past Apple has mostly used Foxconn for production, but there is history between the two companies. Pegatron currently makes some iPhone 4s, and in the past has been responsible for producing MacBook laptops.
Of course, Apple's decision to broaden its manufacturing horizons comes in the context of the Foxconn suicide debacle. Although that issue is starting to fade from the popular light, it is possible that the Cupertino-based company is looking for partners who are not as easily accused of sweatshop conditions. It could also be speculated that this new partnership indicates new Mac desktops are on their way, as both the iMac and the Pro are due for an update.