If you’re serious about this area, you can try to find a second-hand copy of Jurafsky and Martin‘s excellent book: Daniel Jurafsky and James H. Martin, “SPEECH and LANGUAGE PROCESSING: An Introduction to Natural Language Processing, Computational Linguistics, and Speech Recognition”. Second Edition. Pearson Prentice Hall, Upper Saddle River, NJ, USA. 2009.
There is a companion website. The authors are currently preparing the third edition and placing draft versions online. Take a look at that too, but the second edition contains speech technology material that may not be included in the third edition. You may be able to find the PDF of the draft second edition online somewhere, if you can’t obtain a hardcopy.
The original version of Jurafsky and Martin’s Coursera course on NLP (https://www.coursera.org/course/nlp) is not currently available, but you can find the slides here.
If any of the links in the following text are broken, try searching for other versions: this material has a habit of appearing, disappearing, or changing URL.
Dan Jurafsky, with Christopher Manning, also has a course called Natural Language Processing although this does not cover speech technology.
There are other courses on NLP too – try them out and let me know your opinions. For example, you might look at Introduction to Natural Language Processing from the University of Michigan
This is the new version. Still under construction.