One of our family members coming to Thanksgiving is vegetarian. Do I need to cook something special for him?
While you needn't cook separately for vegetarians, it is appropriate and considerate to be sure you make some dishes without animal products. Generally, you can make a great grain or potato side dish for which you don't need chicken stock (you can always use vegetable stock instead). If you have a vegan at your table, that dish should also be dairy- and egg-free. The same is true for at least one of your vegetable dishes. In addition, I offer a bowl of dressed chickpeas along with the green salad, as a way of making that course a little heartier for non-meat-eaters.
If you serve your meal buffet style, quietly let the vegetarian know which dishes are animal-free. For some ideas for meat-free Thanksgiving dishes, see An Inspired Vegetarian Thanksgiving, A Vegetarian Thanksgiving, and Inspired Vegetarian: Thanksgiving Menufrom Cooking Light.