The one I use is Teamwork Projects.
You can also have a look at dapulse.
If you would like me to show them both to you and discuss the differences, PM me.
I've said this previously, but I love dapulse for tracking projects, tasks, who's doing what, etc. Admittedly its name is cringeworthy :) but it's really the best tool on the market because: a) it's super visual and colorful - you can see everything in a glance b) it's extremely simple and intuitive c) you can customize it to work however you want
I use it for everything both at work and in my personal life and am totally dependent on it.
I have been using Teamwork Projects.
Another, more visual one I am testing is dapulse. dapulse is intriguing because I can set up a custom visual look for my work flow.