Various tools for writers operated by the ReAnimus Press crew:

The Science Fiction Novel, by Basil Davenport, Robert A. Heinlein, C. M. Kornbluth, Alfred Bester, and Robert Bloch
How To Improve Your Speculative Fiction Openings, by Robert Qualkinbush

General:

Specific to Smashwords:

The Craft of Writing Science Fiction that Sells, by Ben Bova
The Issue at Hand, by James Blish (as William Atheling, Jr.)
Staying Alive - A WriterModern Science Fiction, by Reginald Bretnor, ed.Footprints on Sand, by L. Sprague de Camp and Catherine Crook de CampSpace Travel - A Science Fiction WriterOf Worlds Beyond, by Lloyd Arthur Eshbach, ed.Anthopology 101: Reflections, Inspections and Dissections of SF Anthologies, by Bud WebsterGalaxy Magazine: The Dark and the Light Years, by David L. RosheimHeinleinHaving Relationships With Characters on the Road to Great Fiction, by Andrew BurtHeinlein in Dimension, by Alexei PanshinSF in Dimension, by Alexei and Cory PanshinIn Search of Wonder, by Damon Knight