INNOVATIONS in online mapping have spurred huge consumer-friendly strides in advertising for home sales and rentals.

If you log on to maps.yahoo.com, you will see that Yahoo allows you to isolate a geographical area and search real estate for your desired accommodation by ZIP code, price range and number of bedrooms and bathrooms. You also can request to see nearby services such as ATMs, gas stations, grocery stores, parking and schools.

Just before Yahoo launched this tool, Kelsey Group analyst Greg Stirling had been predicting one of the large portals or search engines would make such an offering. After all, Seattle-based Redfin had recently created a map-based local search site with advertising.

"The folks that can tackle this on a national scale will create an enormously powerful (and lucrative) vertical. Portals, the search engines, real estate verticals (e.g., home again) and especially newspapers take note," Stirling wrote in his blog at blog.Kelseygroup.com.

Print real estate classifieds were worth $4.2 billion in 2004, said Stirling, citing theNational Association of Advertisers. As consumers use the Internet more for buying homes, that off-line ad revenue will be under pressure, he said.

Software engineer Paul Rademacher, by day an employee of PDI/DreamWorks in Redwood City, created a tool called HousingMaps at http://www.housingmaps.com based on the real estate listings of Craigslist and on Google Maps. His search engine crawls all local Craigslists across the country for housing entries.

"My services take data from the listings of housings and gathers all those things together and puts them all in one map, all 35 cities," Rademacher explained.

Rademacher has no formal ties to Craigslist, but he said his project was done with the approval of the online bulletin board.

When you click on this site, you see a map of the United States and are instructed to click on one of the 35 cities where Craigslist has listings. Clicking on a city, you'll see a little balloon that has links to: for sale, for rent, sublets and rooms listings in that area.

"People looking for housing must look at hundreds of listing, sometimes. It's very stressful," said Rademacher, who is himself looking for housing.

"In the future, we will see the emerging of social networking, space and location services," he predicted.