via NYTimes - excerpts:

Internet Mapping
For Victims, News About Home Can Come From Strangers Online
By KATIE HAFNER
Published: September 5, 2005

In the aftermath of Hurricane Katrina, hundreds of displaced residents and their relatives - along with people like Mr. Sprague - have turned to the Internet for information about a home feared damaged or destroyed. Many are using Google Earth, a program available at the Google Web site that lets users zoom in on any address for an aerial view drawn from a database of satellite photos.

By the end of last week, a grass-roots effort had identified scores of posthurricane images, determined the geographical coordinates and visual landmarks to enable their integration into the Google Earth program, and posted them to a Google Earth bulletin board - the place ZuluOne turned for help.

Most of the images originated with the Remote Sensing Division of the National Oceanic and Atmospheric Administration, which has been posting them to its Web site (noaa.gov) since Wednesday.

Taking inspiration from the online volunteers, Google, NASA and Carnegie Mellon University had by Saturday night made the effort more formal, incorporating nearly 4,000 posthurricane images into the Google Earth database (at earth.google.com) for public use.
[...]

Kathryn Cramer, a science fiction editor in Pleasantville, N.Y., whose Web site (www.kathryncramer.com) has served as a clearinghouse for overlay information, said the effort started early last week when she and a few others wondered about the exact location of a levee break and created an overlay using a photo from the news media.

"We were getting a lot of decontextualized disaster photos that didn't give you a real understanding of what was happening," she said.

In a related online collaboration, at www.scipionus.com, people are plastering a Google street map with electronic pushpins marked with information like "casino boats destroyed" and "minor wind damage." And at Google Maps, posthurricane images are also available for flooded areas of New Orleans.

Of the many lessons learned since the 2001 terrorist attacks, "one is that there is an overwhelming desire for geospatial data," said Mr. Aslaksen of NOAA. "It's become a tool as necessary as a word processor."

See also: Kathryn Cramer's (see above) Katrina Archive with a separate list of posts related to maps:

...my Katrina archive contains all blog posts related to Katrina. The archive page is updated each time I make a new Katrina post, so it would be the best place to bookmark. On the other hand, it contains many images, so on a dial-up connection it would be slow to load. Also, separately, I have an online album of Katrina map images, Katrina Floods New Orleans, 2005.