The National Volunteer Organizations Active in Disaster (NVOAD) website at http://www.nvoad.org/  has pages and pages of useful information for ARES members.  One that struck me as useful is a small brochure in the Resource Center/Donations Management section jointly prepared by NVOAD and the Federal Emergency Management Agency (FEMA).

Entitled When Disaster Strikes, this folder provides sound advice for donating your goods and/or your services to a disaster response.  Although the suggestions mentioned in this publication date from 2007, they are as valuable now as they ever were.   The gist of the message is: Cash donations to a legit response organization are usually best, used clothes donations are often the worst, and, when possible, potential volunteers should affiliate with a recognized response organization prior to arriving to volunteer at a disaster site.