Urban Goats are an expanding movement, as I noted about a year ago. They're being used again at Bunker Hill in Los Angeles to clear weeds and shrubs on a steep vacant lot. Becoming more popular and economical, besides being eco-friendly, these critters are a very sustainable solution when they're managed correctly. Environmental Land Management in San Diego will rent them to you for a fee.
In other areas of the country, they become a source of meat, as well. The USDA has an entire program devoted to critters and urban agriculture.