As Hurricane Katrina lashed New Orleans and the central Gulf coast with winds that blew off parts of the giant Superdome's roof, charities geared up for relief efforts by posting appeals on their Web sites.

"We've been soliciting donations online for several years," said Karen Ogden, a spokesperson for the American Red Cross' disaster fund raising group. "And we've seen a steady increase in online donations [from one major event to another]."

In the past two days, said Ogden, the Red Cross -- which has a "Donate Now" button on the front page of its site -- has raised $100,000 with its online pitch.

"Donations are up significantly today over yesterday," she said.

As in the December 2004, Southeast Asian tsunami disaster, when global relief organizations cranked up efforts to raise funds for the affected areas, numerous U.S.-based groups posted new links and/or pleas on their home pages.

Feed the Children, an Oklahoma-based non-profit relief group, replaced its normal front page with one asking for Katrina donations. So did the Salvation Army, which has a donation link on its home page.

Members of the National Voluntary Organizations Active in Disaster, an association of more than 40 groups, including many prominent religious relief agencies, also pitched in. The United Jewish Communities, Catholic Charities USA, and United Methodist Committee on Relief all offered home page links for Katrina relief donations.

But mainstream Web sites that had jumped to pull in money for the tsunami victims showed no evidence of repeating it here in the U.S. for Katrina's. Amazon.com, which raised more than $14 million for the American Red Cross in January via a donation link on its home page, didn't have one as of mid-day Monday. Nor did Google, Yahoo, MSN, or eBay, all of which hustled earlier in the year to put up donation links on their portals. (Google slapped up an "Information about Hurricane Katrina" link on its Spartan home page, but that led to news sources and stories.)

An Amazon spokesperson said that the online retailer had no plans to post a donation link on its site. "Each case is different," she said. "The Red Cross has essentially given over its entire site to donations. The tsunami came out of the blue, so it was an 'all hands on deck' situation, but the Red Cross has been getting ready for this and getting its message out there for several days."

Although no known fraud alerts -- other than some reports of price gouging in the New Orleans area -- had been issued as of Monday, they're coming, said Audri Landford, the co-editor of ScamBusters.org.

"I would be shocked if there were not scams going on even as we speak," she said. "After 9-11, scammers were busy within an hour."

Any time money is involved -- as in a disaster when people open their wallets to relief organizations -- scams are sure to follow, Landford added. To avoid the inevitable online fraud, she recommended that consumers refrain from responding to any e-mail donation request, insure that a charity is legit by visiting the Better Business Bureaus' Give.org, never open attached files (which often pose as photos of the disaster but are actually worms or spyware), and most importantly, use common sense. "That's actually number one," she said.

A practice of the American Red Cross, however, may fall victim to Landford's advice. The organization, said its spokesperson Ogden, sends e-mail to people who have previously donated to the agency.

"We 'e-push' out to former donators," Ogden said, "by sending them an e-mail telling them how we're responding to a disaster, and asking them to support us."

"In that case, I'd have to change my advice to 'never open e-mail from an organization unless you've previously donated," Landford revised. "But even then, use caution. Never click on a link inside an e-mail message."

Other information about Hurricane Katrina, including reports on its progress and general tips on donating cash or goods to disaster victims, can be found on URLs such as the National Weather Service's National Hurricane Center and the Federal Emergency Management Agency's (FEMA) site.