I recently helped a professor create a digital signature for official letters. You can also easily do this with a camera.
- Sign a clean, white sheet of paper with a broad stroke pen.
- Place the signature on a flat surface and saturate it with light.
- Take a picture of the signature with the camera as close as possible without casting a shadow. In this case, I used an iPhone 3GS with Camera+, a third party camera-control app that provides additional features for editing photos.
- Copy or email the photo to yourself.
- Using Microsoft Word, click on Insert > Photo > File, select the signature photo. Adjust its size accordingly.