Chris Schmandt, the head of MIT Media Lab’s Speech Interface Group, has just made a PDF of his now out-of-print 1994 book Voice Communications With Computers: Conversational Systems available for download in PDF form for free off his website.
Chris was one of the readers for my Generals Exams, and naturally this was one of the books on my reading list. It’s 12 years old at this point, but most of the issues he talks about are inherent in speech communications regardless of the technology. Highly recommended.
(Thanks to Thad for the link!)