Here is a video about what Larry calls a rain gutter garden. I have seen various versions of this, usually involving five gallon buckets connected to a primary water source. While I do not consider it to be the end all of gardening and it certainly is not a natural system, it is an interesting way of managing the watering of a container garden. I think its ideals would best be utilized in an urban garden where there is limited space and the possibility gathering water into a multi barrel or large cistern from a roof top rain gathering system.
At any rate I wanted to put this system out there and see what other ideas it might inspire.