Advertisements:
Monster
Meetic

Stellarium - Free astronomy software

Like Google Earth but for the sky

legal_alien
Just been watching the C5 Gadget show and they had top 5 free software. One of them was stellarium, which is an app to display the sky from any point on the planet and you can click on a star / planet / galaxy to get lots of details about it.

http://sourceforge.net/projects/stellarium/

Only just got it running, but it looks great
RMA
For those interested in this sort of thing "Cartes du Ciel", which despite its French name is also available in in English, can also be downloaded free and I find it pretty good.
Marshbot
Yeah, we use Stellarium every time we sky watch. It's so simple to use, love it! V cool.
GreenTea
"Official" Stellarium website here: http://www.stellarium.org/
legal_alien
The Stellarium main page didn't work yesterday when I posted, so put the sourceforge one instead.
Sourceforge is "official" though. From the Stellarium main page:

Sourceforge is the central website where we collaborate on Stellarium, and where you can be heard too!
It's the download / resouce site but not the glossy user front page. They also have other good apps there - like the wonderfull Audactity
You are viewing a low fidelity version of this page. Click to view the full page.