Some of our perennial readers may remember Walk Score, which we wrote about back in 2007. The website ranks neighborhoods’ walkability on a scale of 0 to 100, based  on a complex, patent-pending, ever improving algorithm that awards points based on the distance from a given address to amenities in a variety of categories, including shops and restaurants. If an amenity is within a quarter-mile walk or less, the address gets maximum points; as the distance approaches one mile, points decrease. One mile or more gets a big fat goose egg for walkability.

If your address scores 90-100, you’re living in a “walker’s paradise!” This means that your daily errands do not require a car. Addresses that score 80-90 still qualify as “very walkable.”

Walk Score has compiled a list of the 138 walker’s paradises in America’s 40 largest cities. Tribeca, Little Italy, and Soho in New York City, top the list, tied with 100 points each. But in the city walkability rankings, San Francisco beat New York, with an overall walkability score of 86 versus New York’s 83.

These points mean something — they’re important. A recent study from CEOs for Cities says that each point for walkability could equal up to $3,000 in increased property value.

These cities’ most walkable neighborhoods share the following characteristics, according to Walk Score:

• A center: Walkable neighborhoods have a center, whether it’s a main street or a public space.
• People: Enough people for businesses to flourish and for public transit to run frequently.
• Mixed income, mixed use: Affordable housing located near businesses.
• Parks and public space: Plenty of public places to gather and play.
• Pedestrian design: Buildings are close to the street, parking lots are relegated to the back.
• Schools and workplaces: Close enough that most residents can walk from their homes.
• Complete streets: Streets designed for bicyclists, pedestrians, and transit.

Among the least walkable cities are Charlotte, N.C.; Nashville, Tenn.; and Jacksonville, Fla. — at the bottom of the list, with a score of 36. But Walk Score identifies “walking oases” even in the least walkable cities.

Now, the site has just released new tools – Transit Score and Commute Reports— that rate addresses based on public transit options nearby and calculate estimated monthly transportation costs and time spent commuting.

Transportation is most families’ second largest household expense, so these new tools are particularly useful for people who are house or apartment hunting, and want to take into account “hidden” transportation costs when deciding where to live.

Now, there’s even a free iPhone app to get the Walk Score for any location, map nearby amenities and get walking directions, and see Yelp reviews of these amenities.

And if you’re looking to find out more about a neighborhood’s  overall sustainability, the Chicago-based Center for Neighborhood Technology just came out with Abogo, a “tool that lets you discover how transportation impacts the affordability and sustainability of where you live.” Abogo lets you see the average household transportation expenses for a household in any neighborhood, and also shows the transportation CO2 impact for an average household, and compares that with the regional average.