Think is a Free Web App created using HTML5, Django, Google App Engine, and jQuery. In Think you can create and view mind maps that are called thoughts.
Touted as a mind mapping application, as can be seen from the screenshot, this supports concept mapping structures that depart from mind mapping’s hierarchical form.
GraphMind is a Drupal module (Drupal is a Content Management System). Notable is the fact that it can import and export FreeMind maps.
I have only found one screenshot, but if this can be taken as a good example, it appears that this is a left-to-right mapper that is closer to being a graphical outliner