You might want to consider Smarthome.com for X-10 parts and cocoontech.com for a forum.
I use a combination of programs:
X10Net for networked control of lights and switches (also programmed to send text msg to my phone whenever security cams are triggered)
VNC for remote access over my network
Remote2PC for remote access over the internet using my pocket pc phone, or CarPuter
A simple X-10 install would incorporate
ActiveHome control software and a few X-10 lamp modules, maybe replace a wall switch and an electrical outlet. The computer software would handle all the X-10 monitoring and automated tasks and any connected pc could log into the one with the interface (remote desktop, VNC, etc) for manual switching. Done, less than $100.