This one is a challenge. I run a business with 4 major projects going on at once. My business partner and I are looking for an online project management solution that can be accessed both from the web on Mac and PC, and via iPhone ideally.

We really like the project and progress tracking in OmniPlan, but that's not offered online. A solid visual representation of deadlines and progress is important.

We would also like something that won't obliterate our own GTD systems? We will also be sharing certain projects with contractors as well.

Thanks for any advice you can offer!