Thanks for your response, Craven.
dotproject looks good. That's definitely on our top 3 list now. We keep debating, however, whether we want a full-featured program, or just a todolist/bugtracker. If we set up something like dotproject, we almost have to use the calendar, etc. which is a much greater redesign of our office flow than simply to implement a communal task list.
We really like the look and feel of
Roundup, too. But none of us have used python. And I need to make sure you can put due dates on somewhere.
We also like
phpbugtracker.
I think all the programs email you notifications when you've been assigned a task, and allow you to respond/discuss via email. I'll probably come up with other important factors before I launch.