Go to Legal, as well.
When you create a photograph, a copyright is also created for the photograph, automatically.
You need not register the copyright.
But if you register the photograph, and your copyright is infringed, you have a much stronger case when negotiating a settlement or in court.
And, you can sue for statutory damages and legal expenses.
Registration is easy, and hundreds of photographs can be registered at the same time.
Copyright on the Internet Franklin Pierce Law Center, by Prof. Thomas G. Field, Jr.
Copyright Procedures: A Tutorial Peter Krogh
Example of a Creative Commons License Attribution-NonCommercial-NoDerivs 2.0
Electronic Copyright Registration for Photographers Allen Murabayshi
Fairly Useful - the Fair Use Blog Matthew Sag
Fair Use of Copyright Lee Wilson
Understanding Fair Use Carolyn E. Wright
National Press Photographer's Association:
Plagiarism Today Blog