Windows/Mac/Linux: Free application Colabolo is a simple, lightweight task delegation tool designed to assign, organise and track team task collaboration.
Colabolo has a lot of advantages for team task collaboration. For starters, it's an Adobe AIR application, so it works virtually anywhere. It's set up to look kind of like a desktop email application but for tasks. You can organize your tasks by type, status, priority or by the person you assigned to it; view updates in the Colabolo inbox without dealing with an email inbox overflowing with updates; comment on and update issues collaboratively; and review project progress with a nice dashboard, complete with snazzy graphs.
Colabolo may not be perfect for every team situation, but for simple task management for teams, it does the trick. Jason over at Gizmodo has been using it and loves it because "it's lightweight" and doesn't have the "obscene amount of features in normal task management systems". If you've been overwhelmed by giant collaborative task management apps in the past, this one may be worth a try. Colabolo is a free download for Windows, Mac OS X, and Linux, requires Adobe AIR. iPhone and iPod touch owners may also be pleased to know that an iPhone version is coming soon.