Keep in mind that though humidity may help with cold and cough symptoms, it could make asthma/COPD worse if you have it.
Here are some compact humidifers that can be placed on a nightstand near the bed.
Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids. Google+ Christopher Chang, MD Bio