Rain barrels operate under similar principals to rain gardens. Instead of having a vegetated depression to collect water, though, a large barrel at the end of your downspouts collects roof runoff. Rain barrels have covers with small openings to collect the water, but which don't allow mosquitos to breed.
Water collected from rain barrels can be used to water gardens and lawn without having to use town or well water from a hose. They can be especially useful during periods of drought. Some towns offer discounts on purchases of rain barrels through their Departments of Public Works or Conservation. Check with your town hall today!