http://actioncenter.drugpolicy.org/action/index.asp?step=2&item=28232&MS=KatrinaRelief-101105-aa
The letter from the website is copied below. You can customize your own version. I added the two sentences before the dotted line -- I figure it's good to show them some different text right up front so they'll see it and realize someone put more thought and effort into sending it than just filling out their info and clicking "SEND."
Yours in liberty,
<<< Starchild >>>
Americans like myself are tired of paying for a failed War on Some Drugs. In the face of the Katrina disaster, it's about time to put some of that money toward more productive uses that actually help people.