from Xbox live:

We’ve cranked up the volume for Xtival ’08 with 72 hours of controlled mayhem that you’ll never forget. Xtival is a three-day party that’s FREE for EVERYONE on Xbox LIVE; even Silver members will be able to experience the thrill of multiplaying with their friends – all weekend! So get your friends together and enjoy LIVE to the max. This year brings exclusive new music videos, HD movies and new games to download. You can chat to our headline act The Prodigy, and take advantage of multiplayer using FIFA’s new 10v10 feature. Above all else this is your chance to play your favourite games with your mates – like there’s no tomorrow!

from 28 to 30 november 2008.

LINK (english site)

The xbox live site is available in many language, please check your country.