As I mentioned briefly before, the heating in my house is controlled by a server, running linux, obviously. I use the devices from elv.de to control the temperature in the rooms, but, when I started the system there was no way to turn the boiler on and off according to the need for heat in the house, so I developed a script myself, in php, using the FHZ1000 linux server available from here (I haven't upgraded to the FHEM yet, still in the previous version), which reads all data from the system and decides if we need to turn the boiler on or off. I then use an FS20 Switch to control it. But I'll elaborate on that one of these days. The system has been setup for more than 2 years now, with no major glitches or problems, and heating consistently and comfortably. Furthermore, according to my calculations, the system already payed for itself. Of course, I turn the server down every once in a while for maintenance or upgrades, but it is now 122 days, or 4 months since it was last turned on! that means that the whole heating seasons it has been on! I'll try to go up until April when I usually turn the boiler off, without rebooting the server!
For the technically minded, the server is a Jetway MiniITX board, with 512Mb of RAM, a TinyPSU and a 2.5" hard disk, running OpenSuse 10.3. It consumes only 25W of power, in an enclosure made by myself.