A burgeoning grass roots effort to put a roof over the heads of hundreds of thousands left homeless by Hurricane Katrina, combined with official relocation efforts to shelter people in need, could have an unintended, but welcomed widespread ripple effect on the lives of those housed.

Homeless experts say a roof over your head does a lot more than provide shelter from the storm, which certainly is a good start.

But a home also is a sanitary place to store and prepare food and water, bathe and groom. A home provides privacy, a place for dignified respite at the end of a long day, and a location from which to receive regular medical or emergency assistance.

A home is also an address to leave for prospective employers and right now, for the many victims of the storm, a place where you can stay put and reconnect with family, friends and others.

It's all those things, and more, which are easily taken for granted -- until you are homeless.

Among some 250,000 estimated to now be in temporary shelters, many were already poor, destitute, infirm or older and had been left twisting in a wind that left them truly homeless. Now, thanks to an outpouring of people opening their homes, many of them will soon get a much needed boost to their psyche, perhaps an unexpected new shot at the American Dream.

The gift of housing isn't, however, without its concerns.

Not surprisingly, the Internet is playing a huge role, but the Web right away opens a digital divide -- offers of housing number in the thousands, but the people who need shelter often don't have computer access and unlimited telephone time.

Most sites are designed for relief workers and volunteers to match housing with those who need it or print out lists and deliver them to Katrina's victims.

However, the lists of private homes may get snarled in bureaucratic red tape as government agencies and other official relief efforts rely upon their own housing lists and refuse to promote grassroots lists as official business.

The "free shelter" movement is virtually without precedent. Official relief efforts are not likely, in the middle of disaster recovery, to relax the rules and take on the responsibility of so many "volunteer" home or property owners who haven't used established channels.

The Red Cross recently initially denied the City of San Francisco financial support to shelter 300 victims because, it said, the city didn't file the proper paperwork.

Already deep in hot water, the federal government isn't likely to take chances.

And then there's the victim-beware factor. Nothing could be worse than a Katrina victim somehow becoming a "free shelter" victim and leave an official shelter with the promise of housing only to quickly become homeless.

Like so many pop-up ads, Internet and email-based scams are already surfacing. Initially, they claim to be victims, rather than offers for housing, according to the Federal Trade Commission.

There's also concern that those living in donated shelters may not have the rights and protections that come with renting or owning property.

Along with the outpouring of invitations for shelter, hurricane victims also need housing advocates to protect them in their new lives. Home and property owners may want to reconsider what vehicle they use to offer free housing.

For now, hopefully, the benefits of the grassroots housing effort outweighs the risks, but those risks shouldn't be ignored.

Here's a quick rundown of available housing offered by official relief efforts and the grassroots swell of property owners.

Official recovery housing

• The U.S. Department of Housing and Urban Development is spearheading one of the federal housing relief responses with a host of efforts. Beginning with a toll-free number -- (866) 641-8102 -- for those without computer access, HUD's finding vacant multi-family housing, public housing units, and HUD-owned homes in a 500-mile radius of the affected areas for use as temporary housing. It's also tapping its inventory of some 500 Real Estate Owned (REO) properties in several Gulf Coast states. Replacement housing and vouchers will also be available for those displaced from public housing.

• In a related effort, the National Multi Housing Council is directing its members to the Federal Emergency Management Agency's (which now operates under the Department of Homeland Security) housing effort under the auspices of the National Emergency Resources Registry.

• The National Association of Realtors, FEMA and Florida State University's Center for Disaster Risk Policy created Disaster Housing Resources a data bank of housing open to anyone to post information on available housing for occupancy and to anyone seeking housing. The units are rental properties for disaster victims who need a place to go while their ravaged home is being repaired or rebuilt.

• Now a HomeStore.com operation, Welcome Wagon, which for 75 years has helped people connect with their communities, opened Relief Welcome Wagon, an extension of their operations, specifically to help Hurricane Katrina victims connect with people in their communities who can provide housing.

Grassroots housing

• Not long after Katrina passed over the Gulf Coast, the home page of the nation's best known online classified section, Craig's List lit up with pointers to classifieds posted by area for available housing, some free, some at reduced rates, but virtually everywhere in the nation from Rouge River, OR to Manhattan. Some of the invitations come with paid air fare, meals and other assistance. The Web site also has sections on people and pet locating, employment offers, transportation help and more.

• HomeFlood.org provides a database for relief workers to use to connect displaced people with housing. It's also a forum for finding relief effort volunteers.

• Political activists MoveOn.org opened HurricaneHousing.org and is offering housing from property owners in 110 cities.

• Web designers from Provo, UT quickly turned on KatrinaHousing.Org and by Sept. 4 was boasting more than 39,000 "beds available."

• Advance Internet and New Orleans daily newspaper Times-Picayune's joint online venture NOLA.com opened a housing center forum to connect property owners and those in need of housing. The website offers links to other assistance.

• Operation: Share Your Home was created by a group of Shreveport, LA residents who say they believe "the response to the devastation in our state is not solely the responsibility of government agencies" and offer online space to post available housing from donors and online space for victims to state their shelter needs.

• Second home and vacation rental owners are also getting into the act. The WVR Group, including CyberRentals.Com, GreatRentals.com and , A1 Vacations.Com opened up webpages for those with vacant vacation rentals to loan to displaced Katrina victims.