5. Turn an old system into a Folding@Home system
Here's an upgrade for any older netbook or notebook that's not only easy, but gives you an opportunity to help a worthy cause.
Folding@Home is a project developed at Stanford University. Once you download the client, your computer becomes a "node" on the Stanford network and runs scientific calculations to help researchers understand protein folding and, in turn, to find cures for cancer and other diseases.
If you're particularly ambitious, you could set up multiple old computers as Folding@Home clients. The software lets you determine the percentage of computing resources you want to dedicate to the research and even when those resources will operate.
I used a Toshiba Satellite 4600 laptop as a research client. This system is so old it doesn't even support current wireless standards, so I added a 3Com Wi-Fi card. Next, I downloaded the client at Folding.stanford.edu and installed it. The app runs in the system tray in the background -- you can right-click the icon to see configuration options.
You can see the scientific calculations running on your laptop, but for the most part the software runs in the background so you can still use the laptop for Web or e-mail. In my tests, the calculations never intruded on my daily activities and only started running after the system went idle -- usually after several minutes. You can even configure how long the software will wait before it starts working and restrict the time to certain hours of the day.
Folding@Home isn't the only distributed computing project that will run on older computers. There's a list of some others at Wikipedia.
6. Use any netbook for home security
Netbooks are too slow to handle gaming and movies, but they work great as home security devices. They can show you who is at the front door or even detect motion and alert you to an intruder. I used a Lenovo IdeaPad S10-3t with 1GB of RAM and an Intel Atom processor to find out if a new webcam could support motion detection on an old system.
I installed Yawcam, a free Web surveillance application that supports motion detection and video recording. Setting up Yawcam is easy: You first install the app, then select the built-in webcam for your netbook. You can set up the software so that it sends you an e-mail whenever it detects motion.
Another option is to install a dedicated Wi-Fi security camera, such as the D-Link DCS-1130. This camera mounts to an exterior wall and then feeds a video signal over a home wireless network to your netbook. That way, you can see who is at the front door right from your netbook, no matter what room of the house it's in.
The motion detection with Yawcam is extremely accurate. In my tests, I could make just a slight hand movement in front of the screen and, within a few minutes, receive an e-mail alert on my Apple iPhone.