The President gains broad powers to employ the military domestically, I believe, in H.R.5122, S.2767 which apparently became law on 10/17/2006. The lefties I work with (and they compose 95% of my colleagues) are all atwitter. It does appear to be the end of Posse Comitatus.
The use of the military in a pandemic has been discussed ad nauseum in some of the meetings I've attended. These guys think that the military are a) stooges of Bush and b) have God-like powers to solve problems with food/water/power distribution and to quell civil unrest. It would be funny if it weren't so sad. (For instance, I heard one otherwise sensible scientist say that the military could take over electrical generating stations if the operators were dead/ill/MIA. There's an MOS for "Operator, electric generating plant, coal-fired", right?)
Cite
(Sec. 1042) Revises federal provisions allowing the President to utilize the Armed Forces in connection with interference with federal and state law to allow the President to employ the Armed Forces and National Guard in federal service to restore public order in cases of natural disaster, epidemic or other public health emergency, terrorist attack or incident, or domestic violence. Requires the President to notify Congress within 14 days of the exercise of such authority. Authorizes the President, when exercising such authority, to direct the Secretary to provide supplies, services, and equipment to persons affected by the situation.