Since this is actually becoming a FAQ

[truepenny]

Thus far, there are four published Booth stories that are not in The Bone Key:

• "The Replacement." The Willows 2.3 (September/October 2008): 48-54.
  
• "White Charles." Clarkesworld Magazine 36 (September 2009).
  
• "The World Without Sleep." Postscripts 14 (Spring 2008): 40-64.
  
• "The Yellow Dressing Gown." Weird Tales 63.2 (March-April 2008): 63-69.

I intend to keep writing Booth stories--I'm working on several right now, for very loose definitions of "working"--so eventually there should be enough for a second collection, but it's not one of those things where you should wait under water.