I checked every programming book I have on my Kindle: Hillegass's Cocoa Programming, Odersky et al.'s Programming in Scala, and a couple Pragmatic Programmer books -- none "trigger" the monospaced font now supported by the Kindle. I suppose the "good" news is that there are not many programming books for the Kindle yet, so the amount of unsupported content is low.
Now that a monospaced font is available and Amazon is going to make Kindle material open on a variety of platforms (i.e., the iPhone), one hopes that the tech publishers will make the extra effort to support the Kindle / Mobi format. Both O'Reilly & Associates and Pragmatic Programmers have an eBook infrastructure and high-quality texts. It is just a matter of whether they can be convinced that the incremental cost of supporting the Kindle format is worthwhile.