Screenwriting : Story development/brainstorming - cloud/online tools? by Darren Vukasinovic

Been looking around at various collaborative story development tools, but can't quite find anything that fits the bill for "green fields" story development. For writing I generally use Celtx, and for developing ideas I generally use a lot of different tools, from Trello to keep me organized (to-do) to just Google Docs and Dropbox to store assets... I'm developing a story that is in early development stage with an overseas colleague and trying to find something that will help kind of mind map, store ideas/web references/documents, and let us build up character profiles and timelines.. about the closest I've come is things like SpiderScribe as an interactive "pin board" in this rough development stage. Anybody got any suggestions? Am I just after some kind of nirvana that doesn't (yet?) exist! Happy to hear what other people use to rapidly develop core story premise (plot, timelines, characters, etc.). Thank you!