Emergency Communications

I've not seen reporting that corroborates this, but supposedly volunteer geeks were able to re-establish on-the-ground communications within weeks of Katrina using Mobile Repeater and Mesh Node backpacks (think portable wifi array, deployed by foot).
 

  
 It seems likely that the Federal government could have responded as quickly, if they had the interest or the manpower (the National Guard was elsewhere, if I recall correctly), but this is impressive. Apparently, disaster relief organizations (and the military) have been using similar systems for some time.

An interesting alternative to centralized infrastructure (public or private).