How do I include links to Worldcat, or Library Thing?

This is another step specific to input filters that I will definitely add to future documentation.

When you open up an input format, like Filtered HTML, from Administer->Site Configuration->Input Formats, you should see a "configure" tab. Toward the bottom of that tab there should be a section for the Book Post module. Check which links you want to appear, save the configuration, and you should be all set.

This is behavior similar to all input filters but it is still pretty unintuitive to find...