If you want to be able to use workshop particpants' stories as examples in the future, you need to have them sign a release form.
This form allows participants to choose from a list of release options. For example, a participant can choose to share his/her story as a teaching tool in workshop settings, but not to have it posted to the web or shown at conferences.
This form was orginally designed for Silence Speaks participants, so many of the options included specific references to violence prevention work, ie "I consent to show my story at anti-violence, public health, and social justice conferences, to generate support for the work of Silence Speaks." These references have been removed so you can tailor the form to the needs of your project.