Generally speaking if you have proper semantic markup, you really shouldn't need to style for non-visual users. That just leaves print, and including a print stylesheet would depend on the nature of the site and its contents.

But for speech/aural, braille, and search engines, if you're markup's not getting the job done for them, there's something wrong with your markup. Just be sure you're not sending your screen media layout stuff to those users by setting media="screen" on your LINK.

Another detail the front-end framework morons oft seem to either be blissfully unaware of, or simply don't care about.