If you are going to publish your photographs online then you might want to check out this site I am using. WaterMarquee is an online tool that allows people to watermark images to protect their copyrights. You don't have to install any application to complete this task. You have the option to add text or image as a watermark also, like your logo or signature.
It's simple and easy to use and its free! Try it out and see what you think~http://www.watermarquee.com/