A SIP is a planter watered from the bottom... 2-liter soda bottles would be a perfect fit for my kitchen windowsill for next winter's indoor garden. Just have to make a slip over cover to make them all pretty.
DIY hanging planters - (the link is for purchasing) - this is easily a DIY project - made with two liter soda bottles painted and holes punctured and threaded with fishing line, or even "jump rings" through the holes and decorative chain to hang with. So cool!
DIY herb gardens. Cut the soda bottle or any plastic bottle with a cover. Turn upside down; attach to board. I'm thinking of leaving the cover to the bottle on; punch in a few holes to drain excess water, but not have the soil drain out also. And even better if you can make wholes in the board so you only see the plants!!!!