During earth hour on the 28th of March switch off the TV as well and take the opportunity to look up at the night sky. Both Jupiter and Venus should be prominent during Earthhour and with a good pair of Binoculars (10x50s) you should be able to see Jupiter's moons. 

Here is a link to the Jodrell Band web site which has decent sky maps and things to look out for.

http://www.jb.man.ac.uk/astronomy/nightsky/