Disasters really are the ultimate DIY setting - stakes are high, centralized solutions are often insufficient, overwhelmed or disabled, and volunteers and donors are everywhere. Often you'll see new communications tools and practices go through major transformations - Americans didnt initially take to cell phones as fast as the rest of the world, but that all changed after 9/11.
I spent a lot of time studying the role of communications in disasters a few years ago when I was doing research at NYU's Center for Catastrophe Preparedness. I wrote a report, which I think is still a useful reference
"Telecommunications Infrastructure in Disasters: Preparing Cities for Crisis Communications"
Some other examples:
Sahana - http://www.sahana.lk/node/12 - general purpose open source disaster response toolkit
KatrinaList - http://discovermagazine.com/2005/dec/emerging-technology - good article by outside.in founder Stephen Johnson on how the Katrina victim and refugee lists were coordinated using Web 2.0
What other kinds of problems could DIY disaster response solve?
One thing that occurs is that none of these are particularly mobile friendly frameworks. There are loads of SMS alerting schemes out there, but most are top-down, intended to be used by authorities to alert large groups of residents. Are there any p2p disaster messaging platforms out there?