People say it's important to give your audience a sense of what they can do to be part of the solution, so that they don't leap from avoiding the troubling message about climate change directly to despair that nothing can be done.
So in the spirit of "at least we can do this now" I offer these tips for cutting the carbon footprint of our internet habit:
#1 Find or buy a couple of power bars that have an on/off switch. Set up one to control all your small device chargers: cellphone, PDA, laptop, Wiimote, whatever. It turns out those little "brick" transformers in chargers draw a small amount of power whenever plugged in to the wall, even when the battery-powered product is not connected(!) Clue: they stay warm all the time. If it's warm, it's functioning as a tiny baseboard heater. Save needing to plug and unplug the AC prongs by just flipping the switch on the power bar. During heating season it's less critical.
Set up another one at your computer, and plug into it all the computer peripherals you use only occasionally, including the power "brick" converters for small DC power supplies.
Leave the power bar switched off except when you need the devices. Both Macs and PCs can cope with having USB devices powered off and then turned on when needed.
If you have a router and DSL or cable modem, but you are the only user, consider if you can power these down when you're not online. They typically need no more time to sync up with your ISP than your PC needs to boot up, or come out of hiberate. (For wireless routers, this will be less appealing, but see if you can work out some plan - switching off while you're out of the house, while you sleep, etc.) Leave as little as possible powered on 24/7.
#2 Windows users: set up your PC to enable hibernation, using the Power options control panel. Then download and run this simple registry update, which tells windows to make visible the hidden Hibernate button in the Shut Down/Restart dialog box. Page explaining the registry change and link to download the .REG. Don't be alarmed by browser warnings about dangerous file type. I've tested this download, and it does what it says.
The hidden hibernate button can already be revealed by pressing "CTRL" while the box is showing, but why keep it secret? Out of sight is out of mind.
When you hibernate, Windows saves a snapshot of what's in memory, right down to what files and web pages you have open. It can then power down your PC completely. When you power up again, it does the usual BIOS 'POST', then when it starts from your hard drive, it sees the hibernate image and reloads that instead of booting windows from scratch. Loading is considerably faster, and you're back where you left off. (You'll still need to use "restart" to complete some Windows updates, security patches, etc. at times.)
I believe the appeal of this little tweak can help steer us all to take advantage of Hibernate, where we'd otherwise be tempted to leave the PC on for many hours ("I can't bear to watch it 'saving your settings' for 5 minutes, and then wait for Windows to boot when I want to get back online later") Also perfect for laptops - great for battery life. Hibernate is "off", while standby is "on but low power" and still drains your battery gradually.
You can set the Power Options control panel to hibernate your PC automatically after a chosen interval of inactivity, just as you've likely got already for screen saver and/or standby.
By itself this tweak won't save the world, but little steps in the right direction, taken by enough people on enough different fronts, can make a good start.