I was looking for a party game that we can play tonight at the New Year's party and I saw a lot of people looking for something to spice up a dinner - here's what we did last year.
Basically it's an adoptation of the tv show 'the mole' (well that's what it was called here in Belgium anyway). The idea is that there is a group of people with one of them being 'the mole' (as in: someone who tries to sabotage the rest) and one of them is 'the mole-catcher'; all the others have a 'mission' that came with the invitation to the party. The 'normal players' have to try to do their mission (they can't tell anyone else what that mission is!), the mole has to try to prevent them to do their missions (he was given a list of what missions there were but not who was given which mission) and the mole-catcher has to try to figure out who the mole is, what the missions are and who had to do which mission.
The missions are something like:
- try to drink from every one of the guest's glasses at least once during the evening
- turn the volume on the tv up and down 5 times
- tell 5 jokes that make at least 5 people laugh
- steal 5 forks

During the evening, the host (who is not part of the game) will have a few rounds of 'guessing who's the mole': everyone gets a piece of paper and they have to answer a number of questions about who they think is the mold: what's his/her shoe-size, what kind of car does he/she drive, ... If, at the end of the evening, a couple of people have succeeded in completing theirs mission, the answers to these questions will be used to find a winner. Of course at that time, the 'mole' will have to reveal himself, after the 'mole-catcher' has had a chance to say who he/she thinks was the mole and what missions everyone had to do.

I hope the explanation is a bit clear, I don't have much time at the moment because I have to organize a game myself for tonight and I don't have any ideas yet, but if you have any questions ask away and I'll try to answer next week. It's a great game because it can span the whole evening, it's not 'dominant' (in that you can a normal conversation during the evening about something else than the game) and yet it can be used to fill the 'empty moments'.

It worked out great, I was the mole last year and my girlfriend had a sneak peek at my 'mission' paper so she knew which wasn't supposed to have happened, but still it was great. It wasn't too disruptive (a lot of games require 100% attention which can get in the way of socializing and catching up) yet in quiet moments everyone had something to do or to think about.