There are various x10 vendors, some which may not spam. The cm17a firecracker seems an ideal x10 controller to use. There are some past post on the subject. A liberary file (x10firecracker.zip) has been posted for use with the arduino, but I haven't had a chance to try it.
However, when I looked up X10 controllers, they were around $20 per switch. If I can buy the other solution for $5, I need more reasons to go with the more expensive solution. Maybe I'm looking in the wrong places. Of course with x10, I would only need a centralized controller on my laptop or desktop, and not a separate microprocessor.
And maybe the x10 company is no longer as bad as they used to be (I have one supplier I bought an $8 cable from, and they've been sending me 3 or more emails/day, and while I block some, they keep morphing the address so it gets past the filters).