I have used X10 modules on assorted lights and devices for home automation for several years, and although the remote control facet has always worked well, tying the system into my Linux boxes has never been easy. Numerous small, typically one-person X10 controller projects have come and gone. But one application has survived: Heyu. It runs on desktop Linux machines without requiring the overhead of a Web or database server, and it enables direct X10 control, event scheduling, and more.
For those not familiar with it, X10 is a protocol designed to transmit short serial messages over household electrical lines to plugged-in devices -- in practical usage, often a simple "on" or "off" to toggle power of a lamp or appliance plugged in through an X10 receiver module. Radio frequency (RF) remote controls are the most common way to manually control the devices, but manufacturers also make serial port adapters so you can use your computer instead.