X10 is one of many lighting control standards that LinuxMCE supports. We also support:
* EIB / KNX
and many others.
What you need, depends on the particular lighting buss, you wish to find. Google is a good friend here, and can help you find stores that sell these particular devices.
Depending on the lighting system chosen, you will need to get
* modules for each light, either in the form of plug-in modules for lamps, or switches for light fixtures.
* a Master Controller
* a Computer Interface
Once you have these things, you can configure LinuxMCE to use them via the Setup Wizard, or the Web Admin.