Trello looks pretty good, will have to have a deeper look.
Realtime updates are deceptively complicated to get right. I bumped that whole branch of development so I could get something out (really try to work some of the ideas of Lean and the Minimal Viable Product).
I've had a look at the site, but not signed up as I have had a pretty clear vision for storywall that I wanted to get out in the last couple of weeks.
What do you think of trello?