If, as the old saying goes, "we read to know we're not alone," why is it that the minute we turn the final page of a book we love, we long to tell others about it?

So we start book clubs, talk to friends about books, and, increasingly, we turn to social networking Web sites designed with readers in mind. Here are some ways to get in touch with other readers online.

Paperbackswap.com

This is another well-established book exchange community site; its members exchange more than 30,000 titles every week. The site even offers printable postage. It also has two sister sites, SwapaCD.com and SwapaDVD.com.