Tagg.ly allows Users to Watermark Photos

Fast Company:

Watermarking can still be cropped out by someone who aims to actively steal the photographer’s work–but that’s another problem for another day. In the meantime, a solution for the accidental erasure of credit and attribution for a photographer’s work is a good start.

This is an easy app to use but don’t expect it to prevent someone from stealing your work. A dedicated thief will get it regardless.

I’d only use this app for “branding” or promotional purposes. In that light, it works nicely as seen here.