It's that time of year when the "which humidifier should I buy" requests start coming in. I wrote about the Honeywell HWM-500 last year at this time — its UV germ-killing feature addresses the main problem with most humidifiers — if you don't clean the tank often, bacteria growth can actually make the air in your home less healthy. The Honeywell is still a great option, but I'm adding the Air-o-Swiss Travel Ultrasonic AOS 7146 this year. The compact Air-o-Swiss is designed for travel — instead of a dedicated water tank, you use an ordinary plastic water bottle — so all you need to carry with you is the small base unit. And instead of cleaning the tank, you just recycle and replace it. Buy it for $49.99 at Amazon.com.