The daddy of project management, Basecamp was created when 37 Signals couldn't find a project management app that wasn't insanely complicated, and so decided to build its own. It worked so well that clients wanted to use it, too, and things grew from there. Featuring a whole suite of collaborative tools including to-do lists, wiki-style documents, file sharing and messaging, it packs just about everything you need to keep any project running smoothly. You can use it via the web or with iOS and Android apps, and if you want to get a feel for it you can sign up for a 60-day free trial.

Scribblar has live audio chat capabilities. Scribblar is more like a chat room - it even has audio available - and as such it is very useful indeed. Creative brainstorming and artwork revision can be collaborated in the 'room' you create. It's an effective online collaboration tool and is available for free.
It has the following functions:
 Online training and tutoring
 Revising artwork and images
 Creative brainstorming
 Sales and product demos
 Interviews and tests