For Linux I Have the Following Hardware
CM11A
W800RF (via Serial to USB Adapter)
I would say those are the 2 minimum things that you will need
The W800RF32 receives:
* All 256 house/unit code addresses
* All regular X10 RF commands (on, off, dim, brighten, etc.)
* Extended 32 bit RF commands, such as those transmitted by X10's “Entertainment Anywhere” remotes and X10 security modules such as the DS10.
I use Misterhouse for automation and some perl apps that use a special binary for misterhouse where applications can send commands to the CM11A directly.. like A1 on A1 Off. Misterhouse even allows you to relay the commands received over the W800RF to the CM11A.
Check out my blog for more. Feel free to email me. Misterhouse is my main automation software, AHP is my backup.
http://shiksa.dyndns.org/~nswint/2005/12/home-automation-101-for-my-automation.html