Can I offer a couple of examples that might serve to illustrate? One online and the other on campus.
I worked as an online tutor team half in the UK and half in China. We tutored on an online course together as a highly distributed tutoring team. We each had a group to care for and to try and maintain some sort of cohesion as we went through a very strange but exciting experience, I started a blog in the tutor-space. I kept the blog throughout and the other tutors annotated it according to aspects they agreed or disagreed with. So we worked inside this one diary as a way of checking our understanding over time. That for me was collaboration (apart from designing the course together as well).
Currently I'm using voting technology on campus to get students working as a group reflecting together. It's a process of cooperative inquiry using a snowball/pyramid discussion technique to generate a whole-class view before voting. That always feels like very close collaboration (see http://www.sharedthinking.info for more on this).
So for me its not tools because you can do something collaborative with almost anything. For me it's about being genuinely collaborative. Thanks for the prompt to participate Emma. I'm always enjoying these discussions.
Faculty of Education
University of Glasgow