If interested in nature photography, I found an awesome site that explains everything from the best type of equipment, to the effect flash photography has on nocturnal birds. There is even a nature photography forum to talk to other photographers whether they be professional or beginners.
On the site, composition is explained by breaking it down in an image in order to “see the compositional elements”. I think this is a great explanation for new, interested photographers. If you are having difficulty grasping the art of good composition, I suggest reading more about it on Photo.net
Another helpful category they cover on the site is “Photography of the Sun, Moon and Stars”. They go to explain the best lenses for the job along with what to do and what NOT to do. Also included, are links to sites that can help with other sky photography.
Photo thanks to Theregoesducky.blogspot.com
If you enjoy nature photography and would like to learn the art, I suggest checking out Photo.net. They have a ton of information and can link you to even more related sites.