The best free site I have found (so far) for editing pictures and adding text to them is www.picmonkey.com .
When editing your photos please make sure:
- The font colour and size you select is easy to read against the background of the image
- You add a photo credit/created by credit in the bottom right hand corner of your image
- Just to be safe, you e-mail your final edited picture to yourself and you save them on your folder on the net work.