Zen Koans

I was reading this ' Zen for Beginners' and came across this ' Koan' which is very imporant in Zen practice. And very popular Japanese item, like ' Haiku'.
A koan (pronounced /ko.an/) is a story, dialog, question, or statement in the history and lore of Chan (Zen) Buddhism, generally containing aspects that are inaccessible to rational understanding, yet that may be accessible to Intuition. Koans are often used by Zen practitioners as objects of meditation to induce an experience of enlightenment or realization, and by Zen teachers as testing questions when a student wishes to validate their experience of enlightenment. Here's the wiki link , to start with :

http://en.wikipedia.org/wiki/Koans

Gateless Gate is a Koan ext. link, which has some 31 Zen Koans.

http://www.ibiblio.org/zen/cgi-bin/koan-index.pl

These koans, or parables, were translated into English from a book called the Shaseki-shu (Collection of Stone and Sand), written late in the thirteenth century by the Japanese Zen teacher Muju (the "non-dweller"), and from anecdotes of Zen monks taken from various books published in Japan around the turn of the 20th century.

http://www.ashidakim.com/zenkoans/zenindex.html

List of Koans from China Page dot com, one page site, neatly made.

http://www.chinapage.com/zen/koan1.html

A very good list of zen koan collections, both classical and modern, with hyper links , is found here.

http://www.ciolek.com/WWWVLPages/ZenPages/KoanStudy.html

Very interesting , one page article on ' unconditioned Buddhism and Zen', here :

http://www.buddhistinformation.com/unconditioned__in_buddhism.htm