I just returned from a very unique experience: 2 weeks on the Gulf Coast of Mississippi, helping design and deploy a wireless network to provide free Internet connectivity to communities that were devastated by Hurricane Katrina. The work was very challenging and very rewarding, and I strongly encourage anyone who can to consider going down and helping out for a week or two.
I was working with Radio Response, which is an ad hoc group formed in the wake of Katrina, mostly out of the WiFi ISP industry. There's a lot on their web site about what they've done, and what they still want to do; in particular, check out some of the press clippings about the organization.
Networking in a disaster zone is a fascinating challenge. You have to figure out how to make the best of what you've got, because getting more (whether it's equipment, service, or personnel) can be very difficult. There are all sorts of unique obstacles (logistical, safety, infrastructure, political, environmental) to overcome or bypass. On the other hand, you can pretty immediately see positive results from your work.
One thing that surprised me (but probably shouldn't have) was the extent to which we ended up serving other volunteer groups, rather than the victims directly. We were able to provide Internet connectivity to multiple volunteer groups who were running kitchens feeding thousands of people a day, a mobile trauma hospital, the main warehouse distributing donated food and other relief supplies throughout the area where we were operating, a couple of FEMA Urban Search and Rescue (USAR) Task Forces, and various other organizations. Most of these organizations had other, more limited methods of Internet access, but by providing them with connectivity that was generally faster and of higher bandwidth, we were able to make their jobs that much easier (by more easily allowing them to far more easily coordinate with their support organizations outside the disaster area, for example), which meant they could provide that much more and better service to the victims of the disaster.
Anyway, as I said, the work was both very challenging and very rewarding, and I encourage you to consider donating time or resources to Radio Response or other organizations who are doing relief work. The level of devastation in the region is simply staggering; entire communities have been wiped out, and are being rebuilt from the ground up. New Orleans tends to get the vast majority of the public's attention, but it's far from the only area to be devastated by Katrina and Rita.