I'm posting a series on using social networking to promote books,
based on material from my new book,
Yahoo Groups are similar to LinkedIn Groups, and there is some overlap in both topics and participants. Some groups have fewer than a dozen members, some have thousands. Some participants are experts and some are newbies. If you write nonfiction, find some questions to answer. Point out that you’ve written a book on the subject that provides even more information. The signature of your message can provide links to your booksellers, website, blogs, Facebook page, etc.
(below) Yahoo also provides an Answers service where anyone can ask or answer anything. As with Yahoo’s groups, you can answer a question to build credibility and provide links to websites that sell your books.