I came across this timeline today. Pretty infuriating to think that so many unnecessary deaths took place when they did not have to.
August 23 - The U.S. National Hurricane Center (NHC) issues a statement saying that Tropical Depression Twelve had formed over the southeastern Bahamas.
August 24 morning - The storm system is upgraded to Tropical Storm Katrina.
August 25 - The storm is upgraded to become the fourth hurricane of the 2005 season.
August 25 6:30PM - Katrina makes its first landfall in Florida as a Category 1 hurricane. At least 11 deaths in Florida are attributed to the storm.
August 26 - Louisiana Governor Kathleen Babineaux Blanco declares state of emergency.
August 27 - Katrina is upgraded to a Category 3 hurricane.
August 27 - New Orleans Mayor Ray Nagin calls for a voluntary evacuation of the city.
August 27 - President Bush declares a state of emergency in Louisiana
August 28 12:40AM CDT - Katrina becomes a Category 4 hurricane.
August 28 10AM CDT - National Weather Service issues a bulletin predicting "devastating" damage.
August 28 10AM CDT - Mandatory evacuation is ordered for New Orleans City.
August 28 1PM CDT - Katrina becomes a Category 5 hurricane with a highest sustained wind speed of 175 mph and gusts up to 215 mph.
August 29 6:10AM CDT - Katrina makes second landfall near Grand Isle, Louisiana as a Category 4 Hurricane, with maximum sustained winds of 145 mph
August 29 - Katrina makes third landfall near Louisiana/Mississippi border.
August 29 - AP: "FEMA director] Brown also urged local fire and rescue departments outside Louisiana, Alabama and Mississippi not to send trucks or emergency workers into disaster areas without an explicit request for help from state or local governments."
August 30 1:30AM CDT - CNN reports that a levee on the 17th Street Canal, which connects into Lake Pontchartrain, suffered a two city-block wide breach. It is later reported that a total of three levees are breached.
August 30 10PM CDT - New Orleans Mayor Ray Nagin announces that the planned sandbagging of the 17th Street levee breach has failed.
August 30 - 80 percent of New Orleans is underwater.
August 30 - Many instances of looting reported in the city of New Orleans.
August 30 - FEMA refuses to allow volunteer firefighters into New Orleans.
August 31 - The U.S. military starts to move ships and helicopters to the region at the request of the Federal Emergency Management Agency. August 31 - President Bush heads back to Washington
from vacationing in Crawford, TX. Though he does not stop in Louisiana, Air Force One flies over the Gulf Coast so that he can view the devastation. 
August 31 - The U.S. military starts to move ships and helicopters to the region at the request of the Federal Emergency Management Agency.
August 31 - President Bush declares Gulf Coast a Public Health Emergency. 
August 31 - Governor Kathleen Blanco of Louisiana orders that all of New Orleans, including the Superdome, be evacuated.
August 31 - New Orleans's 1,500 member police force is ordered to abandon search and rescue missions and turn their attention toward controlling the widespread looting and a curfew is placed in effect. Mayor Ray Nagin calls for increased federal assistance
August 31 11PM EDT - U.S. government weather officials announce that the center of the remnant low of what was Katrina has been completely absorbed by a frontal boundary in southeastern Canada, with no discernible circulation.
September 1 - President Bush President tells ABC's Diane Sawyer: "I fully understand people wanting things to have happened yesterday" (ABC)
September 1 - Governor Blanco says that the death toll may be "in the thousands".
September 1 - The shelter in Houston's Astrodome is ruled full and could not accept any more people.
September 1 - Homeland Security Secretary Michael Chertoff announces that 4,200 National Guard troops trained as military police will be deployed to New Orleans over the next three days. Louisiana Gov. Kathleen Blanco requests the mobilization of 40,000 National Guard troops.
September 1 - California swift water rescue crew units each rescue hundreds in Orleans and Jefferson parishes
September 1 - FEMA halts California swift water rescue crews from conducting further rescues.
September 3 - Ted Koppel on ABC News Nightline interviews FEMA Director Brown who declares that FEMA only became aware of crisis at the superdome on this date. Koppel questions how FEMA could not have known that 1,000s were without food, water, or toilets for days.
September 4 - The Superdome is completely evacuated.
Second week aftermath
September 5 - The 17th Street Canal levee breach is plugged with 3,000 pound sandbags and truckloads of rock.
September 6 - Forced evacuation of New Orleans ordered by mayor.
September 6 - "Hundreds of firefighters who volunteered to help rescue victims have instead been playing cards, taking classes on the history of the Federal Emergency Management Agency and lounging at an Atlanta airport hotel for days while they await orders." Some had been waiting for four days.
September 6 - Some firefighters handed their first assignment: "to stand beside President Bush as he tours devastated areas."