uMarkOnline is a very simple and easy to use webapp. It is Windows based and all you need to do is to simply upload your image or images and type the word or words you want to watermark. Once you enter your text you then have a few more options like bold, text size and italics. Once that is done it comes down to choosing a color for your text - use the color picker and location for your watermark. The image will update in real-time with your changes. once your done use right-click to download your image and it's now ready for use.
Try UMarkOnline now for free.