I have lots of images to be watermarked. Is there a good batch image watermarking application that can do the job quickly and easily. I have found some, but none of these have a professional touch.
Lightroom does this very well, plus it will handle other exports steps simultaneously.
It is very easy to do. Just enable the watermark section in the Export dialog. You can use image or text and adjust transparency, position and scale. All the watermarks on Neopanoramic which you can see here are generated by Lightroom. You can contrast this with service-side watermarking, see for example my gallery here. The latter is done using a PNG image with transparency, blended via PHP before being cached.
While you can find other watermarking solutions, not all will optionally resize (using a variety of constraints), rename (using customizable patterns), sharpen, etc the images which you are preparing. It is usually uncommon to watermark images without going from other normalizing steps, at the very least resizing.
What's a "professional touch"? :).
In the end you really have two approaches to creating a watermark: 1) Create an image and overlay that in a specific size over your image, either covering a specific percentage area or located in a specific spot. 2) Create a text overlay that is automatically added to your photos.
Both can be done with various tools and unless you have a specific clear description of what you want to do, there is no way anybody can recommend something that you'll consider appropriate. For my part, I can tell you that Lightroom has the ability to watermark images, including as a batch process. Another option is to create a Photoshop routine that will automatically apply a watermark to your images, however I have found that I need to distinguish between landscape and portrait in Photoshop.
Having said that, I suspect the majority of watermarks you find on the web, will be a png image designed once and then overlayed over the image - sometimes with transparency sometimes without, most likely with Lightroom in many cases.