It was recently published a free software to draw watermark texts on images. This tool can help to protect your pictures because it's able to generate semi-transparent text on images.
This online program is powerful and can be used to draw several kinds of texts over your photos (not necessarily watermarks). You can set the text disposition, font, size, color, transparency and other useful graphic elements. Other important feature is that text is always drawn with professional anti-aliasing.
It's free, fast, very easy to use and available online. Try it at this Online Digital Watermark Text page.
Below you see a photo with several sample watermark texts drawn. You can see the image in real size by clicking it. Notice the very high quality of text drawing, even with semi-transparent and diagonal rendering.