You can immediately file for a refund on last year's taxes. You'll need an itemized list of losses, but you'll need that anyway.
The IRS will be out at the disaster sites. I just talked to a friend tonight who will be going. They can't do anything for you at the site, except guide you in the process.
Also, do not just walk away from property. Talk to your accountant first. If there is a loan on the property, and you let the mortgage company have it, they can "forgive" that debt. Debt forgiveness is taxable income.