In my mind one of the greatest applications for the NIT's is as a controller/interface for home automation systems. Wireless, high resolution touch screens that can run whatever software you dream up, all at a very reasonable price. There are lots of Linux-based automation systems out there, with various hardware tie-ins, etc, but since people have asked I'll share my setup here, some of the options I've explored beyond it, and leave the table open for other ideas and other people's experiences.

My setup:
Lighting controls - Insteon Powerline-based automation.
Insteon is like the old X10 equipment, but with a lot more up-to-date thinking and planning behind it. There's no wireless involved, no extra cabling; all you do is replace your light switches/receptacles/etc with Insteon-compatible equivalents, and they communicate over the existing powerline wiring; no need to worry about interference/etc, it just works. Devices are easy to program and "group" with a "click 1, click 2, done" sort of approach, and are reasonably priced (switches are about $40-50 Cdn, slightly lower in USD; this is half price of some of the other technologies like Z-Wave). A variety of external interfacing devices are also available, ranging from simple "powerline to serial port" PLMs, to "powerline to webserver" modules, all at varying price points. You can get pre-rolled windows software, or go with one of the existing linux-based solutions; if you're feeling really adventerous (as I was) you can even write your own serial interfacing code.
Alarm System - DSC Power832 with IT-100 interface module
In Canada DSC panels are some of the most common, dirt cheap little alarm panels around. I work for an alarm installation company, and trust me, these panels are not the best things to ever exist, but they work for basic purposes, and work quite well with the serial interface module (IT-100) which provides a very straightforward interface for computer control (and documentation to back it up!). I really use the alarm system as a means of "telling my house" when I'm there and when the house is empty, so that it can do things like ensure lights are turned off, adjust thermostat, etc whenever I'm not around rather than on a time basis.
Thermostat - HAI OmniPro
Great little thermostat with a serial port built into it for external control. Unfortunately these guys are pretty hard to come by these days as HAI seems to have moved to a "buy out giant system or nothing" approach, but there are other alternatives out there I'm sure. Thermostats are really just a temperature sensor and some relays, so worst case scenario is you can always use a serial-relay board or some Phidgets to achieve the same results.
TV/Media - Fedora 9 Box running Mythtv
- Fedora 9 Box acting as networked PulseAudio Sink for outdoor speakers.
MythTV is a great little media setup, though it does have some short comings. The integrated web interface though can be quite handy, especially on the N8x0 since you can actually use it (good luck on an Ipod). Apps like Irreco are also great for controlling it. I've got a second Linux box setup on an old low power machine downstairs that just acts as a PulseAudio sink, connected to my backyard speakers so that when you play music on the MythBox, you can have it play in the room, or inside and outside (that whole summer party effect).
Overall Automation/Control System - Rob's Homebrew project... shhh!
I wrote my own network oriented automation system, that allows for communications and sync/event management between the various systems in the house. It's still a work in progress, but it does do quite a bit thus far. However that's just me, I like to do things my way. For most people some like LinuxMCE or MisterHouse is a far, far better approach for this (LinuxMCE also offers you prebuilt orbiters/etc for tablets).

Anyways, thats my setup in a nutshell; the nice thing about it is that all of the hardware components are locally available (If you're Canadian, this is a big plus), and of course all of the software is open and as crazy-customizable as you want to make it.

I was thinking of using Mr House. Do you have any experience with it?

In CA the utility company, PG&E, has a program to install remotely controlled thermostats in homes so PG&E can cut back on power consumtion to prevent blackouts -- they adjust the temperature setting a few degrees and then restore to your normal program. Side benefit is that you can use the Internet to program your "SmartAC" thermostat. They even gave me a $25 rebate on my bill for letting them install it.

How do you get a "SmartAC" ? I live in Fremont if that makes any difference...

Try here https://www.pgesmartac.com/login.jsp. They may be phasing the state and Fresno is a heavy user of electric because of AC and many days over 100.

Not available for a while yet, but this sounds attractive and considering the source may work with the tablets out of the box.

bro there is already a project like this that you might want to take a look at LinuxMCE www.linuxmce.org