It's often difficult to track down works by libertarian writers, and, as often as not, more interesting works come with a substantial price tag attached. Specialized publishers like AK Press, Charles H. Kerr, M&S Press, and the Liberty Fund have reprinted lots of low-cost classics for their respective audiences, but it's rare that publishers have the means to publish everything radicals would like to see. Academic reprint companies have brought out a number of generally very expensive editions, which don't help much. So it's interesting to see quite a few very interesting, but decidedly marginal texts from the tradition appear from scattered and frequently equally marginal sources.
Stephen Pearl Andrews' Discoveries in Chinese is available from Elibron (as are nearly all of Samuel Butler's works, including the hard-to-find stuff on evolution, in either paperback or eBook editions.) William Batchelder Greene's The Blazing Star and the Jewish Kabbalah is also available from an occult publisher in paperback. Kessinger has publisher Bolton Hall's Gift of Sleep, along with Three Acres And Liberty, and copies of a Loose Leaf Press edition of Halo of Grief are available various places online. Josiah Warren's Written Music Remodeled and Invested with the Simplicity of an Exact Science is apparently available in a print-on-demand edition from Astrologos, which isn't cheap, but is sure likely to be more usuable than the microforms i've seen.
These are all works by libertarian authors, all very interesting, but somewhat distant from those authors' core concerns. What's interesting is that they seem to be potential bridging points for other audiences.