One of my favorite artists Joseph Arthur offers a new track "Last Train to Ithaca" dedicated to the victims of Katrina. [mp3]
Arthur encourages donations to Mercy Corps. Also visit the In the Sun Foundation, launched by Michael Stipe. REM collaborated with various artists on Arthur's song "In the Sun" to raise money for hurricane victims. Sundance is airing a brief documentary about that effort. You can watch it online.