Used Clothing
Plenty of organizations will accept your tired attire, but Vietnam Veterans of America resells it to fund programs for veterans, and will pick up your donation.
Business Attire
The Women's Alliance provides a directory of local organizations that accept interview-ready clothing for disadvantaged job-seeking women. Men's suits can go to Career Gear, which is based in New York City and has affiliates in five other cities.
Winter Coats
Hold on to them until fall, then find a local coat drive through One Warm Coat (most drives begin in October). Coats must be clean, and all closures should work.