The Numark iDJ2 iPod DJ Mixedr gives you a professional mixing console as well as docking capabilities:

“The iDJ2 features a fresh and innovative new iPod docking system that allows users to play two songs simultaneously from a single iPod, without the need of a computer. Users can also hook up multiple mass storage devices including additional iPod’sâ„¢, Memory Sticksâ„¢, and external USB hard drives through rear panel USB ports. In addition to USB connectivity, the iDJ2 comes complete with line inputs for any audio source including a microphone, CD players and turntables.”

Source. Via OhGizmo.