PhotoBulk is an OS X app that should interest webmasters, photographers and anyone who must manage and edit a lot of images.
PhotoBult can watermark images, bulk resize them and optimize photos by reducing file size. It's all very fast, and the app supports a variety of formats including JPEG, PNG, GIF, BMP and TIFF. Photoshop's native format is not supported, and the optimization routines only support JPEG and PNG.
I put the app to work on some of my landscape photos, and found it speedy and reliable. First I tried the watermark function. I could set the font type and size, and drag it anywhere on the image. I could also set the transparency (by the way, if you are setting a copyright symbol it's Option-G on a Mac).
The bulk resize function also worked well. Take your image, and input a new number of pixels for width and height. Optimization also worked well. I chose the default setting, and found that my JPEGs were reduced about 75 percent in file size with no obvious change in quality. When I magnified the image to 300 percent I could see a slight increase in noise in the shadows.