Oldonyo L'engai, Tanzania
As with most disasters, the best way to prevent a Katrina-like catastrophe is preparedness. The best successes in volcanic mitigation have been in places where the combination of monitoring, communications and practice fit together like so many legos in a set, allowing for a calm and orderly evacuation when the eruption, or signs of eruption, began (e.g., Rabaul in 1994). This is why it is always heartening to me to see articles about places trying to implement hazard mitigation plans for their volcanoes. Two examples are in the news today:
(1) Officials in Indonesia have 1,000 volunteers ready to assist evacuees if Semeru continues erupting. Indonesia is one of the worst combinations for natural disasters: heavily populated and highly geologically active. However, Bagiyo Setyono of the Communications Division in the Malang Regency sums things up perfectly: "Just follow the instructions." (Try to not get too caught up with the descriptions of the volcanism at Semeru in the article - I think something got lost in translation).
(2) USGS scientists from the Volcano Disaster Assistance Program (VDAP) will be assisting people in Tanzania get prepared for the eventual eruption of Oldonyo L'engai. The problem is a combination of volcanic risk assessment (a must), evacuation plans, disaster preparedness and monitoring. Previous eruptions of Oldonyo L'engai (the world's only known carbonitite volcano - yes, it more-or-less erupts baking soda, so cool that it is black, not red when molten) have caused significant damage to the local water sources and livestock grass.
I'm sure there are many more examples of volcanic mitigation and monitoring going on worldwide, but the more attention that is paid to these endeavors, the more the general public will appreciate their value.