Specific to the Kinect, you'll want to be sure to get the older-style (non-slim) XBox and Kinect because you won't be able to get enough current over an extended USB run to power the Kinect. The version for the older units has a separate external power supply whereas the one for the slim XBox has a special connection that combines USB and power.

If you need a long run, it might get expensive (~$350+) for something like the Gefen EXTUSB20LR USB 2.0 Extender.