I always have a cool mist humidifier running in the nursery. Can't prove whether it helps, but I figure it can't hurt in the dry climate where we live. Crane makes some really cute ones. I have the penguin:
http://www.amazon.com/Crane-Adorable-Gallon-Humidifier-Penguin/dp/B000GWJD0A/ref=sr_1_1?ie=UTF8&s=home-garden&qid=1294943863&sr=8-1

My daughter was born in August and we added a humidifier to the nursery when the weather got colder and she started getting a dry nose. It definitely helps. We like the Crane ones too..we have this one: http://www.amazon.com/Crane-Shape-Gallon-Humidifier-Green/dp/B0026IC2A0/ref=sr_1_1?ie=UTF8&s=home-garden&qid=1294943959&sr=8-1-catcorr

We needed a cool mist vaporizer pretty early on. The breast milk can get thick in newborns' throats, and at night it sounded like our daughter had a smoker's cough by the time she was just two weeks old. The vaporizer cleared it up immediately. Now we use it in the winter months to help keep her skin moist. I can't remember why, but "cool mist" is important when you buy one. Eventually, you'll need one. Maybe not as early as we did, but for sure by the time they get their first cold.

I've used one before, but they are always a pain to clean. However, after hearing this last week, I've given them away! You may want to read/listen to it. But either way babies LOVE ceiling fans!
http://www.npr.org/2011/01/07/132743646/Humidifiers-Dont-Do-Lick-Of-Good-Helping-Colds

We use one every night, and even for naps. We started because our little one had a stuffy nose, but kept using it. We noticed she slept MUCH better when we had it on. <---we can only guess it's because of the white noise. Bonus is she hasn't had a stuffy nose or really a cold since we started using it months ago. She's now 7 months! So it gives you more benefits than just a white noise machine.

We recently moved to a much drier climate than we're used to. We've since started running two humidifiers all day and night. One is in our bedroom (co-sleeping toddler), one is in our main living space. I definitely feel like they make a difference or I wouldn't keep them running!

I have used a cool mist humidifier for my first kid...they are a pain to clean and they need to be lean in order to be healthy. BUT we recently moved and hadn't reno'ed yet-my son was in a bedroom with wallpaper. When we finally got the paper removed we found MOLD underneath it...only and exactly above where the humidifier had been. GROSS! I stopped immediately. I hear vaporisers are better. Just something to be mindful of. Mold=yick. and more sick!

I think they really do help when baby has a cough, but most of all I just love the white noise. It's better than the noise machine we have, and helps keep the dryness down in our house (we shock each other and everything we touch sometimes!). You can get them without a filter, so no worries about mold building up.

We live in WI (same climate) and got one as part of our daughter's nursery set-up. We used it for a couple of days when she had a cold but honestly, that was it--two days in nine months and it didn't even seem to held her cold much. It probably depends on how sniffly your child ends up being.

This was just posted on NPR
http://www.npr.org/2011/01/07/132743646/Humidifiers-Dont-Do-Lick-Of-Good-Helping-Colds
Though I have to say I've noticed a difference when my daughter has a cough. I feel it helps...but whatevah...

When the air is really dry in the winter, it dries out the throat when you have to mouth breathe due to a cold. Dry throat = more sore throat. We use humidifiers all through the winter to prevent nosebleeds due to dry air. Humidifiers may not help colds go away sooner, but they certainly make the air more comfortable.

We live somewhere very dry and I don't think it does anything whatsover. If you want white noise, get a white noise machine. They work better.

We've been using a humidifier since my little one's first cold (around 3 months maybe?) and have used it nearly every night since. The white noise is the main reason, but the cool mist helps as well. She is 13 months old now and has only had a runny nose/cold twice in her life. (knock on wood)

Another fan of the Crane Humidifier, here. We have the Penguin (two of them actually) and I DO think they help a lot during colds. I use it for myself, too, when I have a stuffy nose. We used to have another one, but it was a pain to clean and the filters would get yucky after a day or two and I'd have to buy new ones. The crane is SO much easier to clean. I just rinse the whole thing with water and a little bleach every other day while we're using it and then I store it with the screw top off so it completely dries out between uses. Good luck with the new baby! ENJOY!

Thanks everyone for all of the great suggestions. I think we're going to go with the Crane teardrop since it seems that at the very least, it can't hurt. The animals are super cute but we might steal this one for our room at some point. :)

we run the humidifier every night in the winter. It's good for white noise and she gets a snotty nose from the forced air heat otherwise.

I grew up in a house so dry that I would have nosebleeds or bloody crust boogers (sorry for the description, but that's what they were!). My parents put in a humidifier and my goodness, what a huge difference in sleep quality. No more nosebleeds or sore throats.

I'd say if you're worried, get a hygrometer to measure the humidity in your home. You want to aim for around 45%, give or take 10%. You do not want to get over 60%, because that's when mold grows.

You also want to place the humidifier near the middle of the room, so the humidity can spread out. If you stick it in a corner or next to a wall, you're more likely to run into those mold issues.

I was once told by a doctor that when your nasal passages are dry and cracked, you're more susceptible to colds. True? I don't know. But it's more comfortable for us when the humidity isn't too low, and we all seem to sleep better, whether we have colds or not. (I'm in Chicago, where it's VERY dry right now. My son had his first-ever nosebleed yesterday---yikes!)

I'd suggest getting a humidifier that has a demineralization cartridge of some sort, because otherwise you might get the "white dust" on surfaces in your home if you don't use distilled water. Filtered water is not enough. It was a nightmare to clean the white dust off of everything; it even made its way inside closets. Ick. Our humidifiers have been the Crane ones (frog, penguin, a plain one, etc.) and we're very happy with them.

this is def a grand question for your pedi. i live in south texas gulf coast region. although were about 45 mins from the beach/gulf were still very humid here! so really no need. we do use a white noise for both kids rooms. its WONDERFUL! congrats on your new baby.

We got a cool mist humidifier for our first child and it did seem to help her, but it also made the room so cold even on a low setting. It was just a regular size humidifier from the pharmacy, not one of the small or animal things marketed for kids. Has anyone else experienced this? We stopped using it after she got blue toes and fingertips. But now we have our second and winter is really doing a number on her. I'd love to know if it's worth getting the thing out of storage.

From a recommendation by my allergist (MD) and primary care doctor (DO), I use a space heater and forced air evaporative humidifier with humidistat in the bedroom. Even my new CPAP machine has a heated humidifier included.

Being in a humid climate, I also run a stand alone de-humidifier year round too. Just be careful not to have the humidification you're adding to the room be taken out by a de-humidifier. I'm looking forward to owning my own HVAC system just to have the whole-house effects of good humidification control.

Also, from experience working in the IT industry, humidifiers help in keeping the static levels down.

definitely! we're in chicago in the city and have 1 for each of the kids (3+ and almost 2) - crane elephants. they get stowed away around may and i usually get it out around october when someone brings home a cold. i think it does help loosen the mucus and i swear they sleep better when it's going full blast and they're either coughing or all stuffed up.