Eugene Ionesco's Rhinoceros - http://vzone.virgin.net/numb.world/rhino.home.htm Information on the play itself, recent productions, and the Absurd Theatre.
The Theatre of the Absurd - http://www2.arts.gla.ac.uk/Slavonic/Absurd.htm Describes the etymology of the term and its historical development.
No Exit - http://www.nyu.edu/classes/keefer/hell/sart.html Full text and analysis of Sartre's play.