This may not be your thing... but just in case

Earth Hour
8:30 p.m., Saturday, 27 March 2010

It's sort of fun - turn off your lights for an hour.

Me? In the past I've broken out the oil lamps (strangely, I've got quite a few!).
Candles also work.
Or you can just wander around in the dark.

For what it's worth: this is a rather potent reminder of just how different our world is from that of our not-too-distant ancestor's.
London's Savoy Theater, built by D'Oyly Carte to showcase the operas of Gilbert & Sullivan, was the first public building lighted with electricity - in 1881!

... and I am reminded of a remembered quotation from a high school history text to the effect that Socrates would have felt more at home plopped down in 18th-century Philadelphia than would Ben Franklin if plopped down in 20th-century Philadelphia.
Technology had not advanced much from 5th-century BCE to 18th-century CE (2300 years) - lighting was still all based on fire, 'horsepower' meant just what the word says, oars and sails provided a ship's motive power.

Just for fun, spend an hour in the 18th century - turn off your lights at 8:30 p.m. tonight.