Cork comes from living cork oak trees, and the trees are unharmed during the harvesting process.  The tress produce cork for an average of 150 years!

After harvesting, the cork is left outside to cure for a few weeks to six months.

Then the cork planks are treated with heat, water, and fungicide.

The outer layer, which is of poor quality, is then scraped off.

For the next few weeks, the cork is stacked in a dark cellar, with controlled humidity, to dry and cure.

The cork is then ready to be used for final products.

See the following link for more information:

http://www.ask.com/bar?q=How+is+cork+made%3F&page=1&qsrc=0&dm=all&ab=6&title=How+cork+is+made+-+Background%2C+History%2C+Raw+Materials%2C+The&u=http%3A%2F%2Fwww.madehow.com%2FVolume-5%2FCork.html&sg=WeHhq7bMhIO8CQMpqxaw3S1SWNKDzsB%2BitstGTJKhJs%3D&tsp=1258486474160