Motorola has decided to allow individuals to download their extremely powerful home automation for free. Their software was used in the 2006 Home of the Year award winner for Electronic House Magazine for example.
Unfortuantely Motorola has discontinued support of the application that they had purchased from Lantronix, but has made the excellent decision to allow access to the full unlocked dealer edition(supports far more websites, serial ports and so on compared to the standard edition). They've also decided to allow access to their driver development kit, and a thriving community is continuing to develop drivers for this extensible environment (Insteon and UPB for example).
You can get the software from Motorola at premisesystems.
The Motorola support forum is now only read-only, but is still online.
The community that is quite active in Yahoo groups.
For those that have been looking for a very powerful and extensible environment, but have been put off by the pricing, check out Premise for a possible solution. I've been using it for a little while (since it's free release) and I'm really enjoying it's integration into my home.
EDIT: sorry there are no URL links, I'm too new a member to AVS to post URL's, I'll come back and edit after I've posted a couple more times so that the restriction is lifted. Hopefully you'll see this as usefull information rather than some spam issue.