I learned about this Hurricane Sandy volunteer opportunities map from the EV Grieve blog. The opportunities are mostly located in the East Village. If you know of similar maps for other areas of the city and metro area, please include a link in the comments. Thank you.
Also, consider volunteering your time and skills and donating money. Here is a Boston Globe collection of photos of the hurricane's damage (hat tip: kottke.org via Gelatobaby). Missing from the Globe collection are photographs of the Bronx; Curbed is carrying one of the South Bronx submitted by a reader.