David J. Peterson and Sai Emrys of the Language Creation Society, through whose auspices the Dothraki language was created for HBO’s Game of Thrones, are the subject of an interview at Tor.com. Quite a lot of interesting details about Peterson’s linguistic training, his approach to creating the Dothraki language, and an exclusive new piece of Dothraki (for the phrase “blood of the dragon”) with an accompanying MP3 file.
David and Sai can both be found at the Dothraki forum at Westeros.org, if you have any additional questions for them.