Good story in eWeek about some of the Microsoft efforts around Katrina.
Microsoft Brings .NET to Katrina Relief Effort
A group of Microsoft technologists quickly deployed to contribute their time and talent to the relief effort, and decided to develop a Web site and supporting applications to help Katrina evacuees reach out to relatives and friends and also enable families to locate people they have not heard from since the hurricane hit, said Jim Carroll, chief architect and project manager for the system, known as KatrinaSafe.
The calls for help inside Microsoft went out and were answered incredibly quickly. Robert Scoble has more on similar efforts here.