Our kid is a month and half old now. Until recently, He had been having stuffy nose and breathing problems. On a friend's (Thanks Ravi) advise, I got home a humidifier (cold air one). His breathing has gotten better now and this stuff really works.
I recently purchased a nifty wall clock (for under $10) at Walmart that had a thermometer and a hygrometer. Now I can monitor the humidity level, turn the humidifier on/off based on it.