Many houseplants benefit from sitting in a humidity tray especially during the winter months when our homes are heated and the air can be quite dry. You can go out and spend some money of trays specifically designed for this purpose but if you're smart you can hack a humidity tray out of anything that will hold some water. For example a Tupperware container that is longer than it is deep, cutting out the bottom 2-3 inches of an empty milk jug, the tops of bottoms of take out containers or saucers that may have come with a pot. Just fill whatever container with enough pebbles so that it reaches the rim and then fill with water.
As the water evaporates it raises the ambient humidity around your plants-you may have to refill the water in the tray once a day if there is a lot of sun or it is particularly warm in your home. The one thing you want to look out for is that the bottom of your pot (and roots) are not sitting it water. This can be deadly as excess water contributes to root rot. Make sure your pebbles are high enough to make sure this doesn't happen.
Yesterday while eating a pizza I began to wonder about the person that invented those plastic mini tables that are placed on the center of a pizza to keep the box from coming in contact with the cheese and toppings. Eventually my mind wandered to the possible uses for this plastic thing and I realized it could be used in humidity trays to keep your pots up and off the water eliminating any chance that your plant roots will sit in water (see attached image) and rot.
I still don't know who invented this thing but I'm going to keep thinking of uses in the indoor/outdoor garden for this thing and will post about them as I come up with them. If you can think of any fee free to leave a comment.