BlueLava is a simple CGI script which will let you access Heyu over the Internet to control lamps and appliances in your home.
Heyu Web Interface is a web browser based CGI by Kris Beazley aimed at making Heyu a little more user friendly.
domus.Link is a web-based frontend for Heyu by Istvan Hubay Cebrian. The design focuses on separating configuration from actual controls, thus giving the user a simple and user friendly GUI.
Priscilla is home automation software with a web interface by Pierre Doleans. It allows control of devices in the home with X10, infrared, and 1-wire sensors. Users in France can monitor their electric power consumption and cost with the French Teleinfo system. Priscilla is currently in Beta release.
X10 is a control program for the CP290 Interface written by Larry Campbell and enhanced and modified for Linux by Paul Fox.
A series of Technical Articles by Phil Kingery explains X10 technology in detail.
Ido Bartana's website has special value for those interested in making hardware modifications to X10 modules. (Some proficiency with a soldering iron may be required.)
Neil Cherry's Home Automation website contains a wealth of information about X10 and newer automation technologies.