We (chapter) are using https://www.pivotaltracker.com/ for a while for task management.
It satisfies most of requirements listed below.
I didn't try http://todo.ly/ yet, so I don't know which is better or easier to use.

Samat


2011/12/10 Tomasz Kozłowski <odder.wiki@gmail.com>

Dear All!

During our meeting in Amsterdam on Thursday, December 1, we have
identified some areas that would definitely seek an improvement next
year (more information to come very soon, so stay tuned).

One of those things was task management: we are looking for a good,
convenient way to divide tasks, set (inside) deadlines and manage tasks
that will need to be done when preparing Wiki Loves Monuments 2012.

An obvious idea was to find an on-line tool that deals with task
management: unfortunately, I haven't been able to find a free (as in a
beer, not necessarily as in freedom) tool that would suits our needs.

Our requirements for the tool (except those obvious ones) are as follows:
       * it has to be free (US$0);
       * it has to be able to set dependencies;
       * it should allow the users to use their own accounts;
       * it should allow the users to set&change a task owner;
       * it should be as accessible (mobile versions) as possible.
       * it has to be in English :-))

This week, I've went through a huge amount of on-line task management
tools and the one that suits our needs the most is: <http://todo.ly/>.
You can login to a temporary account I've created with my e-mail address
(see above) and the password: TryThisAccount!

Please play a bit with the tool and state your opinions :-) And if you
know a tool that's better than this one, please let us know as soon as
possible!

Thanks,
--
Tomasz Kozłowski | [[user:odder]]