Lots of charities will take clothes contributions. I don't donate to The Salvation Army because of their history of opposing GLBT rights and equality. We donate unwanted items to Disabled American Veterans or The Leukemia Lymphoma Society.
The Red Cross (almost evewry community has one) or a Goodwill store (very common as well). Also many churches in your area have programs to help people in need. Any of these organizations will gladly accept your donation .
Pretty much any charity shop or if you look online there might be other charitable organisations that you can post your unwanted clothes to =].
If you have a lot of Brand named clothes, you can give them to a Platos Closet & you'll get a little bit of money for them!
Salvation army, Goodwill, or a thrift shop. Some will buy your unwanted clothes. But it depends.
Red cross, goodwill, salvation army, big brothers big sisters, & thrift shops.
Platos closet or good will. Any consignment shop