WWL-870 New Orleans is providing continuous hurricane coverage. This signal is widely available across most of the Eastern and Central U.S.. It's being simulcast on several local FM stations and WWWL-1350.
Other reports have it WTNI-1640 Biloxi is also in hurricane mode relaying a local TV station.
And, WFAA-TV Dallas is reported to be carrying co-owned WWL-TV on a temporary subchannel. During Katrina [u]all[/u] the Belo TV stations were reported relaying WWL-TV on subchannels -- so this may be happening in other markets besides just Dallas.