jacomyal/sigma.js — pull request #25 by Raibaz (2012-05-18 13:48:47+00:00)
Title: Added a new node property, 'shape', that allows to draw square nodes by ...

...setting it to 'square'

Not really sure if everything in my pull request covers everything needed to have full featured square nodes and i'm not really satisfied with the label positioning on square nodes (may need some tweaking)