virtual(a): existing in essence or effect though not in actual fact; "a virtual dependence on charity"; "a virtual revolution"; "virtual reality"
So are you actually looking for the best way to create a team that does not exist but does produce an outcome? I think you are already there :-)
Or are you looking for software to support the communication between teammembers in such a way that they really feel to be a part of a team? Then I would look for software that is already integrated with the way of working of your team members (msn, skype, email, subversion) etc