They are great opportunities to get to know coworkers and introduce yourself to upper management.
Of course, you can make the wrong lasting impression as well. Yahoo has listed some of the biggest holiday party mistakes.
The first big error: Follow the mistletoe rule, i.e., don't overdo it with the kisses. Along the same line, don't hit on an intern, coworker or any members of their families.
Mistake number two: Interpret "festive dress" too liberally. Keep it clean and skip the reindeer antlers.
Next mistake: Hog the buffet table or hoard appetizers.
And of course the biggie: Splitting a bottle of anything is an error. Keep it to a two-drink maximum. Overdoing it can lead to the last two mistakes -- dancing on anything but the dance floor and sharing your true feelings about your coworkers.