TSR Watermark Image software, is a free program for personal use that can add digital watermarks to all your images, photos and pictures with the transparency you decide. The program can also resize the images before the digital watermark is added.
* Made the font size matching more accurate, thanks Bobby
* Command line option to load a config file and run, then exit, usage is: WatermarkImage.exe "C:Path toConfigFileconfigfilename.wmi"
* Fixed that the last photo was kept open when batch watermarking all photos - Thanks Kevin
Product page: here