Hello,
I'm asking myselfe if I can use Ethernet, Xbee and a X10 Modem on one Ardunio board. For my understanding this should work but what do you think? This will be my first arduino board so I have no experiences with this hardware. :~
I think it is too complex for your first project. Any one of those is and advanced project in itself let alone trying to do all three. Your main problem is that you will run out of serial ports so you need a mega at least. That is not to mention the memory it will all take.