I've used the PixWrite Tool (original version) and one easy online program!
From the Authors:
Pixwrite is a simple and quick way to add text labels to any image on the web.
Use PixWrite to:
Write on pictures or photographs
Put your name on auction photos to discourage image theft.
Add a comment to point out a defect or special feature.
Add a funny caption to a pet photo or just note the date and time.
Include a message with an image posted to a blog.
Any time you want quick text on an image.
Pixwrite is not a replacement for a full featured image editor installed on your own PC but can be quicker. Also handy if you are away from your own PC. Just grab the image you want right off the web or upload from your PC. Add labels, and once the photo looks as you want, copy to the local PC then upload to your host or blog. PixWrite maintains your image internally using the png image type so there is never loss of quality no matter how many edits you make! (temporary images are removed after 24 hours. so don't rely on this host for linking)
Hint: To create a watermark effect, choose a color with only slight contrast and a bolder font.
* Due to variations in browser rendering and installed fonts, close registration near the image edge may not be possible. For best results, use the position indicator to place text approx 10 pixels from the edge of your image.