BetterBasics via Amazon offers the Sterline Aromatherapy Cool Mist Essential Oil Diffuser for $29.99. Coupon code "3DIFFUSE" drops it to $19.79. With free shipping, that's the best price we could find by $10, although we saw it for $1 less in July. It glows in seven different colors and features automatic shut-off. Deal ends December 23.

Update: The price has dropped to $19.99 before $13.19 after.