Reading through a web site with guidelines for designing web pages for dyslexic users, I realized how valuable these recommendations can be for any audience, not just people with this condition. 
This is a PowerPoint presentation design guide 101:
  • Choose a big, san-serif font
  • Avoid capitalization
  • Apply a calm background, no watermarks
  • Don't righ-justify text
  • Minimize use of italics
  • Keep things short, write in a simple style
  • Use bullets (if you have to), don't write proze
  • Refer to the reader as "you"
  • Stick to narrow columns, text lines
  • Use pictures