I meant to come and post this earlier, because for anyone here in the UK who didn't know about this it's now a bit late. However, I have decided I will post the link anyway. So, here it is: http://www.earthhour.org
I hope everyone it's not too late for will seriously consider participating.
This last bit is what it said in the e-mail I got from Kati with the link in, but I didn't think she'd mind me borrowing it for use in this post.
"Last year it was only Sydney Australia that participated, and their combined efforts had the equivalent effect of taking 48,000 cars off the road. Imagine what we could do if we ALL did this!?!?! Just ONE hour!!! One hour of candlelit family boardgames, or book reading, or some good, old-fashioned chit-chat & sharing of the day's events."