Pretty much anything in the construction industry, carpentry, electrical, havey machine, & demo just to name a few. There will be no shortage of work for anyone of every experience level. First Aid is something else that is good in disaster situations. Hope this helps.
goat
I understand the tendency to 'flood the zone' and have everyone available come in and help it may not be the best thing to do. Every person who shows up has to be taken care of. They will need food, water, a place to sleep, sanitation and they require organizing.
It is more effective to stage them into an area in waves. First in are emergency services and rescue to get, stranded, injured or dead out. Then crews to clear the roads. Also utility workers will fan out to map out the damage and make sure any compromised gas, water, sewer and power lines are isolated so undamaged sections can be reconnected and service restored quickly without casing fires or more problems.
Then come the linemen who work from large to small and trying to reconnect the most people and most important sites, like hospitals, get connected ASAP.
Once the roads are passable damage control crews of carpenters can get in and tarp damaged homes. Movers can extract the contents of homes too damaged to restore in a timely manner.
It will be a case by case, perhaps lot by lot, basis as to how it is timed and coordinated but I don't see much use for carpentry, interior electrical, sheetrock or painting crews on Galveston island at this time. They aren't ready. There are plenty of 'warm bodies around'. Later, once the situation is stabilized, there will be more work than hands.