From the about page:
Cohere is a visual tool to create, connect and share Ideas. […] Cohere is an idea management tool for you to annotate URLs with ideas, and weave meaningful connections between ideas for personal, team or social use.
The site lists the following key features:
For tutorial videos, view Cohere’s screencast page.
An example network is shown below:
Cohere is being developed in the UK by Open University’s Knowledge Media Institute and is available under a LGPL open source license.