Huy kindly took me out to Quận Tân Bình (Tân Bình District, a long way from Quận Một) to visit Mr Phúc, who is the vice-director of Sao Mai Computer Centre for the Blind. We chatted at length about their education projects and web accessibility for people who are (almost) completely blind. In brief, modern screen readers are quite good; the one Mr Phúc uses (JAWS) apparently uses the Internet Explorer engine to figure out what's going on, implying that anything Internet Explorer can render, JAWS can make sense of, including Flash. So apart from the usual web hygiene of standards compliance and good design, I got the impression that there is not much a website need do to be accessible to people who use such assistive technology.
He also had a braille reader, which he told me is lower-bandwidth but higher fidelity, and so is mostly useful for syntactically fiddly things like coding.