Randy Sarafan is the Technology Editor at Instructables, so you know when he tackles a problem like keeping tabs on properly watering house plants, he's going to do it in enviable DIY fashion. Randy teamed his DIY skills with a soil sensor and an Arduino-controlled water pump to build himself a black thumb-proof plant watering system!
Instead of remembering to water my plants when the soil goes dry, I only have to remember to once and a while refill the water reservoir. In this way, I have decreased my obligation to these plants and put it off to a much later date. Perhaps further iterations of this device can be connected to a rain barrel so that I won't even have to worry about refilling my reservoir, and the entire system can be fully automated.
(x1) 8" x 6" x 3" project enclosure (Radioshack #270-1809)
A commenter notes the less technical could get nearly the same self-watering effect without the power source hazards using a piece of nylon wire:
Take a plant bowl and thread a couple of nylon wires through the bottom holes. Let the nylon threads go down into a bowl of water under the plant bowl. The plant will automatically suck up the water from the nylon thread... no electronics needed. :)
So there, you've got two options before you head out for a late summer vacation. Just be sure you have someone to check on the cats/dogs/fish now...unless you've one of these.