At my place of employment we previously used pivotal tracker which is designed around scrum with all its fancy words. The nice thing was it could pull commit comments from github if the commit contained the pivotal id.
However, we needed something a bit more tailored to our needs and settled on:
https://trello.com/
It is a lot easier to see who was doing what (gravatars), easy to attach files/checklists, write comments, have multiple boards and as many columns as we need. Sort of like a "super whiteboard" the posters above mention.
I'd suggest anybody using physical notes/markers to give trello a look.
