While it doesn't allow you to draw a polygon, www.padmapper.com does give you a Google maps representation of Craigslist listings. The potential downside I see

While it doesn't allow you to draw a polygon, www.padmapper.com does give you a Google maps representation of Craigslist listings. The potential downside I see with this involves listings that include intersections or general locations instead of exact addresses; I'm not sure what the site does in that scenario.