Teemu pointed me to their map annotation tool, which I find extremely well designed and simple to use. The annotation is done ‘a-la-flickr’, selecting a squared part of the image and attaching a text to that. Check this out!
ImaNote – (Image and Map Annotation Notebook) is a web-based multi-user tool that allows you, and your friends, to display a high-resolution image or a collection of images online and add annotations and links in to them. You simply mark an area on an image (e.g. a map) and write an annotation related to the point. You can also add a link to the annotation.
You can use RSS (Really Simple Syndication) to keep track of the annotations added to the image or make links on your own blog/web site/email that are pointing to the annotations on the image. The links leads right to the points in the image. ImaNote is Open Source and Free Software released under the GNU General Public Licence (GPL).