Aside from Chocolate, there are a quite a few other foods which dogs may come into contact with at this time of year, which aren't good for them.
Onions (and related things like garlic), grapes, raisins, and avocados are very bad for dogs. Apparently macadamia nuts, Xylitol (an artificial sweetener) and corn-on-the-cob, can also all cause problems.
The issue with onions is also the same for cats, but cats seem less keen to eat most of these items, being obligatory carnivores, and less inclined towards omnivorous habits than canines.
Cooked meats aside, I've always avoided giving any human food to cats, since there seem to be so many ways that we can go wrong. I've occasionally let Talisker, Zev or Kai sniff something, when they seem keen to be involved with whatever I'm eating or drinking. It's amusing to watch their noses wrinkle when given a sniff of beer or coffee.