http://www.ancienttexts.org/library/mesopotamian/gilgamesh/
This goes to the tablets of the Epic, it contains the actually story of Gilgamesh.
http://novaonline.nvcc.edu/eli/evans/HIS101/Notes/Gilgamesh.html
This link is more of an outline of the story with some education background on the history.
http://www.lumenarts.com/main/index.php/performances/the-epic-of-gilgamesh
For those who work better hearing instead of reading, this link has a video of the epic being told, as well as some paragraphs describing the story.