The NY Times reported yesterday that the manufactures of children's cough and cold medicines will voluntarily put on their label that these medicines should not be used in children under 4. Generally, when a company does something voluntarily, it is done to avoid a worse penalty that will be mandated on them, such as recommendations from some FDA officials to ban these medications altogether for children under six. Earlier this year, the FDA released a public advisory that OTC cold medicines should not be used in children under 2, and these medications are now off the shelf. This issue is what to do with liquid formulas that are commonly taken by much older children. On the one hand, these medicines haven't proven any major scientific benefit, and might in fact cause harm. On the other hand, many children find symptomatic relief, and there is really very limited data to determine whether or not the risks outweigh the benefits.
Most upper respiratory infections in children are caused by viruses. These do not require antibiotics and will resolve on their own. Cold medicines generally contain some combination of antihistamines, decongestants, expectorants, and cough suppressants. Antihistamines are really for allergies, and can potentially make upper respiratory infections worse by thickening secretions The expectorants are common, it is unclear exactly whether or not they help. Decongestants are probably the most effective agents to improve symptoms in children and are likely safe in children over 6. Cough suppressants may also help and are also likely safe.
For children younger than 6, caution is likely warranted; though if your child is miserable medications a decongestant or cough suppressant may be helpful and the risk is fairly low. The American Academy of Pediatrics has some good information on their web site.