Reason's Hit and Run blog and Jesse Walker call our attention to an important essay, "Libertarians and War: A Bibliographical Essay" by Anthony Gregory, a writer I admit I was not familiar before. It offers an excellent discussion of libertarian antiwar thought, with lots of links to books, essays and blog postings.
The sort of libertarian who reads this blog will perhaps notice the omission of Robert Anton Wilson, a prominent antiwar libertarian. On the one hand, this is understandable, as Wilson did not write any books devoted solely to antiwar themes or even any essays (that I can think of, at least -- please point to anything I've missed.) On the other hand, antiwar themes are a major component of Illuminatus!, arguably the most important libertarian novel of the last few decades, and antiwar statements permeate Wilson's work. A couple of examples: Wilson contributed a short story, "Von Neumann's Second Catastrophe," to Lewis Shiner's antiwar science fiction anthology, When the Music's Over, and Wilson wrote this in his essay, "Left and Right: A Non-Euclidean Perspective," reprinted in Email to the Universe: "I know I would kill an armed aggressor, in a concrete crisis situation where that was the only defense of the specific lives of specific individuals I love, although I would never kill a person or employ even minor violence, or physical coercion, on behalf of capitalized Abstractions or Government (who are all damned liars)."
I could write a long blog post pointing to other examples.