Here's a really cool product for people who like to travel or who simply forget to water their plants:  DriWater is a gel made of water and vegetable matter which, when it comes in contact with dry soil, will become water.

To use, simply water your plant well then wrap one of these gel-noodles around the base.  DriWater comes in 30 and 90 day varieties as well as other flavors targeted at professionals.