Some people like to organize costume parties (des soirées déguisées) with a theme, others like to dress to the Ninth (se mettre sur son 31), and dancing will be likely at these parties (French people like to dance... a lot!).
It's tradition to kiss at minight under le gui (pronounced hard G + ee = mistletoe), but that's about all the tradition there is about it - and of course counting down to midgnight sharp, when everybody kisses everybody else, cheers, aplauses...
One thing is certain, there will be some Champagne, and possibly oysters (les huitres - mind your liaison "lay zueetr") and foie gras.
Others will just have a casual gathering... go to a good restaurant (better have a reservation) or snuggle up at home, maybe watch TV, which will most likely feature "un bêtisier" (bloopers) and a live pop songs show, musical or a variety show...
It's not unlikely for cities to organize fireworks (des feux d'artifice) or dance (un bal populaire).
Typical greetings are "je te/vous souhaite une joyeuse année", "bonne année 2011!", "que tout tes/vos voeux se réalisent en 2011".
Bonne année à tous, may your 2011 progress in French be amazing :-)
