How to list a charitable donation?

I am a photographer and have photographed several events for non-profit organizations.  I delivered hundreds of digital images to the organizations free of charge.   They provided me with a letter stating they received the images as a donation with an amount of dollars worth.  How do I list these donations on my Federal Tax form? Do I use the "money" or "items"  category?   If the "item" category,  then what types?