I saw a great video on CNN about urban farming and it focuses on vertical farming systems that are built by a company called Green Living Technologies LLC. This is their website.
They build planting systems for roofs and walls where you can plant house plants and gardens. The video shows them building one in the middle of an urban area. The systems are made out of recycled aluminum and you can plant new crops in them or you can use starter plants that the company has already started growing. I love companies like this that are doing their part to improve lives and culture. Pretty soon, there won't be an excuse for not planting a garden. Check out the video.