THE EXCEPTIONAL generosity of Americans in times of disaster -- outpourings of money, goods and services -- is again evident in huge, heart-warming proportions. No one yet can divine how much it will take to rise to the ravages of Hurricane Katrina, but even the great surge of support so far needs to be sustained well beyond the initial emergency phase. According to the Chronicle of Philanthropy, the pace of cash donations as of Friday was unprecedented: more than $287 million in the four days after the disaster hit. In the 10 days after September 11, 2001, Americans donated $239 million. Yet as reported by The Post's Elizabeth Williamson, relief organizations across the country note that the grand response represents only a fraction of what will be needed for rebuilding efforts that are expected to take years. How far will even the most extraordinary help go in assisting countless people left with nothing more than the clothes they were wearing? The challenge to come, said Maj. Dalton Cunningham, the Salvation Army's divisional commander for Alabama, Louisiana and Mississippi, is "when the emotionalism of the event dies."

Where to help? A list of organizations working specifically to aid victims has been appearing in this newspaper, and a running list is regularly updated on www.washingtonpost.com. Individuals and businesses may have other preferred groups and efforts they wish to assist, but a caution here: Contributors should be wary of despicable operators seeking to take advantage of generous spirits. Sound-alike names with questionable addresses, using "Katrina" as a come-on, are best avoided. Simple rule of thumb: If it's not a group you recognize, find one that you do trust. Beware of telephone pitches, especially any that may solicit cash. The Better Business Bureau Web site -- www.give.org -- lists numerous verified efforts.

Organizations seeking or directing volun-teers should be checked out carefully as well. Blood donors should contact local Red Cross chapters. The Web sites of many newspapers in the affected states are listing local organizations needing specific services, ranging from people with special skills to those willing to provide company, care or shelter for victims. In the Washington area, local governments are work- ing to coordinate offers of housing and volun- teer work. A convoy of buses from the District is taking food, water and other supplies to New Orleans and will return with as many as 400 evacuees to be sheltered in the D.C. Armory. Volunteers to assist this or additional area rescue efforts should contact the American Red Cross at 703-584-8400.

For people around the world who have lost contact with relatives or friends, the Inter- national Committee of the Red Cross, working with the American Red Cross, has launched a special Web page. In turn, people in the disaster area can register to inform others of their situations. The address: familylinks.icrc.org.

Decisions on what and to whom to give are personal, but the reasons to help are there for all to see, and will linger indefinitely.