Reusing water requires a water source like those above and then a transport system to put the water where you want to use it. If you plan to do more than irrigation, you’ll probably need to create sediment or UV filters. For rain barrels you should expect an 80% capture rate.

A couple of interesting projects are mentioned in the article:

Monterey Bay Shores, 341 hotel and residential condominium units with a rainwater catchment system for nonpotable laundry and irrigation use, a graywater recycling system, and Low Impact Development designs such as bioswales and porous sidewalks that will capture and treat 100 percent of all stormwater runoff for onsite use and infiltration. The graywater recycling system, which had to overcome California’s regulatory codes to gain approval, will include mechanical and biological waste treatment systems that will treat graywater for reuse in toilet flushing, irrigation and other nonpotable uses.

Sycamore Ten Point Five, in Charlottesville, VA, a mixed-use development including retail, commercial office space and 16 residential units. The system will include three oversize stainless steel domes positioned on the rooftop with a capacity for capturing and storing 270,000 gallons of annual rainwater. This water will be conveyed into the building via a gravity-utilized distribution system for nonpotable use. Water movement and delivery within the building will be controlled through computer programs in order to achieve the most efficient usage. Collected rainwater will be allocated toward toilet flushing, fire suppression, and watering plants in a series of aquatic trellises that will be located on the sides of the building. These trellises, which will make up a permaculture installment, will utilize evapotranspiration to cool the sides of the building.

Even with renewed focus on water issues (via mandate or LEED requirements), reuse of water or even mere collection of water can run afoul of regulations. Nevertheless, making better use of the water, even if only to keep mulch in the beds and surfaces free of puddles requires little to no outlay and is highly recommended for aesthetic and practical reasons.

[Note: The Virginia Department of Forestry provides a good technical guide to garden gardens, including siting, construction, and plant selection.

Finally, I've seen the AquaBarrels in use in the field and at EcoBuild. I found them to be well constructed and the owner quite knowledgeable about SFH and TH installations.]