Screen readers are software programs that enable individuals who are blind or visually impaired to access text and graphics on the computer screen by voice output, enlarged text, and/or with a refreshable braille display. 

Products that are examples are the Hal Screen Reader and Supernova Reader Magnifier (both made by Dolphin), JAWS (Job Access With Speech made by Freedom Scientific), Window-Eyes (made by GW Micro) and the ZoomText Magnifier/Reader (made by Ai Squared). 

See the National Library Service's 2006 Assistive Technology Products for Information Access Circular for more informatiton on these products.