Reports out of New Orleans indicate that water levels have been rising throughout the day and continue to do so. Two breaches in the massive levee that protects the city -- which is largely below sea level -- from Lake Pontchartain are allowing water to pour in.
More information can be found in this thorough Washington Post article and at this Katrina update blog run by a local New Orleans news channel.
To contribute to the relief effort:
American Red Cross - 1-800-HELP-NOW.
UPDATE - this DailyKos diary has a complete rundown of aid organizations positioned to provide help on the Gulf Coast.