Of course I'll recommend my own article on the subject
There was a great discussion following my article on the forums over at CIC
Here are 5 steps to learning good composition. Follow them, and you'll learn a lot.
1. Study different techniques to composing a picture.
2. Look for ways in which you and other people follow those rules.
3. Take lots of pictures.
4. critiquing the composition of your pictures.
5. Take more pictures. Practice makes perfect.