The Texas Tech Master of Arts in Technical Communication and Rhetoric is one of the most respected programs in the country. It is also one of only two technical communication graduate programs offered completely online. I'm just in my fourth class and already interviewing for jobs. I have been very impressed with both the faculty and the students, and love the fact that the Masters and Doctoral programs are integrated. I highly recommend this program for anyone interested in communication, tech writing or digital rhetoric.
Texas Tech's doctorate curriculum is thorough, and should prepare students from any background to be well-versed in technical communication. The cost ($1860 per course for up to 60 credits) is considerable though, and the requirement to spend 2-weeks every May ($1600 per workshop, plus travel) should be factored in when you apply.