These sites are simply tools for searching more than one web site (see next section) at a time. They are great time savers, and I recommend them highly as a starting point for your search.
These websites are all searchable. That means that you can input an author and/or a title, and you'll receive a list of available items.
Some of the likelier auction sites.
Newsgroups have been around much longer than the web. They are free and unmoderated - the net at its best and worst.
E-mail lists are rather like an email version of a newsgroup or bulletin board, and the same rules apply for the most part.
A few places where you can post want lists more or less permanently.
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