Well, for most people Dropbox is a great way to do it, unfortunately I'm on an android tether out in the middle of the wilderness, so it's not an option for me. On my projects I just try to make sure that all people editing files know whether or not I have finished what I was doing on them, then I upload them, let the involved people know and stay away from them until they do their thing, although sometimes certain people will not do what was planned so eventually I will pick back up on the aforementioned file.
PS. I'm glad to see you stepping up to be the leader of this project, as mentioned by the previous team what was lacking from hero6 was a leader and from my own personal experience with many projects the main trait of a leader is to be dependent on nobody and no thing. You have to keep moving on with the project no matter who or what happens and no matter how much it seems like there is nobody interested or helping, eventually they will. They may come and go, but if nobody is ever dependable as long as you are there putting your time and thought into it and keeping the websites alive, there is always hope!
I only tell you this because it is the hard lessons that I've learned after over a decade of being leaders on various projects