Ranger88, I think you've got a point about not knowing exactly what you'll need for a disaster until the disaster comes--but I'd add that, in my experience, it's not absolute--and your experience from Katrina has given you a lot more information now about how and what to prepare than you had before.
I had a similar--but much milder--experience when 2 tornadoes tore through Nashville, where I was living at the time. All sorts of trees down across roads and power lines; we were without power for days; candles and batteries flew off the shelves, etc. But I learned from that, and now keep large quantities of each on hand. Not enough to last for more than a week, but my likeliest survival scenarios are such that a week's worth of batteries should see me through "stage one" of the likelier situations. Part of it is just realistically looking at where you are, and what kinds of disasters are likeliest there, and what their ramifications will be. If you live below Lake Pontchartrain levels in New Orleans--well, we all know what that town's likeliest disaster looks like now. If you live in Manhattan, you probably have to think about terrorism, and creative exit strategies in case you end up with millions of other people stuck on a little concrete island with no means of making food. If you live in the desert, give thought to water. That kind of stuff. Your experience with your survival gear 30 feet underwater was doubtless frustrating as Hell, but at this point, you are an official disaster veteran, and I think you're realistically much better-equipped to prepare than you were last time around. Me, I keep redundant kits of varying levels at home, in my car, in my wife's vehicle, at the office, and in my briefcase. The office kit is pretty minimal--fanny pack and a few full canteens. Car kit is more involved--rucksack with canteens, water purifier, food supplies, cooking gear, change of clothes, tent, sleeping bag--stuff like that. Home kit is the most involved of all, with frame backpack, lots of gear for different scenarios. I'm putting together an extremely-minimalist belt-pack kit for the little day-hikes that my search-and-rescue-expert acquaintances have informed me bring about the great majority of real-world "survival situations." It would be hard for my town to suffer a disaster that would render all of these inaccessible at the same time, unless I myself were incapacitated.
Incidentally, used to be an EMT myself, and I think the advice above is great. The one disappointment I had with my classes was that most were geared toward stabilizing patients until you could get them into an ambulance and to a hospital, and the assumption was that ambulances and hospitals and oxygen tanks would be easy to come by. In practice, most of my EMT work ended up going on way the heck out in the desert or forest, and I could've used a lot more training on things like what to do if you're five days or 30 miles from hospital access. But if there are wilderness-specific EMT classes out there, that sounds very interesting indeed. On that subject, anyone got any recommended reading on advanced-level wilderness medical stuff?
I would strongly suggest a SOLO or WMS or NOLS course though. Some of the things shown in these books can get you in serous trouble if you attempt to do them without certification and even then there could be problems depending on protocols. Even if you do them correctly.