From Knitting for Change come these links on knitting or crocheting as a way to aid victims of hurricanes Katrina and Rita:
Knit for Katrina is making blankets, and has patterns, guidelines, photos, and a forum on it. People from across the US are sending in squares to be assembled into blankets.
Purls of Hope has a beautiful site, with news, patterns, and information on what to send.
Go Knit, also known as Knitting Arts, also has a relief drive going.