If you're a Mac user and don't have Adobe, you can get Easy Batch software from
www.yellowmug.com
This little program, very inexpensive, enables me to watermark my photos by creating the textbox in Apple Paint and saving it as a png file.
Then, it is dropped into a watermark well. Set the size and opacity of the watermark, as well as kb size limitations on the photos. Drag the selected photos from iPhoto into the photo well, and Easy Batch takes it from there. Easy, cheap, works GREAT!
I do it with the copyright notice AND my artisan's credit because I got sick and tired of finding my photos of my creations on other demo'rs sites without permission AND without proper credit (that is another story in itself).