This is another tool included on here which is not free but we think is worthy of inclusion and of your consideration.  Realsmart offers a great deal and was build around the idea of assessment for learning.

Allow your students to build online eportfolios in a very visually and intuitive way.

Provide success criteria and learning outcomes in a very visual way so that students can measure their own progress, they can upload evidence of meeting that criteria and can also recieve feedback.

Here is a link to the Realsmart website.  Click on the third video (Realsmart: your learning portfolio) for an overview of what it can offer in terms of assessment for learning

With a Google Documents account your students can create a document or presentation and then share it with others.  Others can then either directly edit the document or provide comments on it.

The potential for using this for assessment for learning is hopefully obvious.  Either teacher feedback or peer feedback is made extremely easy once the document is shared with those people.

Another very useful thing about using Google Documents in this way is that a Google Document keeps it's history.  Every time the document is revised by someone a revision is kept.  This makes it easy for the teacher and/or student to track and see how the work has developed over time with improvements and with feedback.

The videos below will give you a good overview of how a document can be shared, comments can be provided and revisions can be used:

If you have never tried Google Documents we strongly recommend you experiment with it.  The possibilities for use within the classroom and education are tremendous.  All you need to do is to visit Google, Sign up for an account and  you will have Google Documents.

You would be  well advised to discuss Google Documents with your ICT Coordinator to see if  they can create a Google Apps for  Education account for your school so that everyone in your  institution can benefit and to make sharing and collaborating within your
establishment even easier.