there is a good collection of articles covering every aspect of the atlatl right here on BCUK in the articles section:
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=160
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=161
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=152
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=144
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=142
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=141
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=140
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=139
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=160
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=161
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=152
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=144
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=142
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=141
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=140
http://www.bushcraftuk.com/content/articles.php?action=show&showarticle=139