Gesso" ['d ?? s ? o] is the Italian word for "Board chalk" (akin to the Greek word "gypsum "), and is a powdered form of the mineral calcium carbonate used in art.
http://en.wikipedia.org/wiki/Gesso

Dick Blick Art Materials - Find a huge selection of gesso and related products for artists, including rabbit skin glue and other painting supports.
http://www.dickblick.com/categories/gesso/

Gesso Communications is a marketing communications firm in Halifax, Nova Scotia, specializing in interactive, print, branding and identity development.
http://www.gesso.ca/

Opaque primer for acrylic and oil paintings, on canvas or board. Contains finest bright white pigment. Dries flat and flexible.
http://www.dickblick.com/zz006/23a/

Ridgeman Gesso make high quality archival painting panels made from natural traditional materials for the professional or amateur artist.
http://www.gesso.com.au/