Is there any book exchange website?

I love reading, so sometimes I will buy duplicate books. As I know, there will be many people have old books that they doesn't read any more. And sometime, I will goto find some old books that you can not find them in the bookstore.

I plan to do something help people like me who is willing to exchange their old books or sell the old books to people who really need it.

A website will be created, first of all, it will be limited in the 回龙观. Before this, I hope to learn something from existing website.
This will be a selfhelp website, people will participate in the community. We are in the participate age!


So if you read my blog, and if you know there is such website, let me know.