I'm interested in joining in a collective story again, but to be honest I'm not too crazy about the more spontaneous approach T5 suggests. I've found that stories done like that tend to start with a lot of enthusiasm and then erode until we reach a point where no one knows what to do or where to go. When we started the HR universe that didn't always stop us for too long because, every time it got stuck, someone (usually Euro) took control of the story and closed the main plot in one or two longs posts, so the rest of us could continue writing. This is OK, but I'm not very interested in doing that at this point.
I think the future is in more planned stories, with moments where improvisation can be used, but all in service of one main plot (having too many unrelated plotlines is something else I don't like). Each story should be "lead" by a different person (like I did with the Murder Mystery experiment) who knows the key moments of the plot, and the rest should move within the boundaries of what the leader has established.
Also, I've never liked "Secret Files" threads. I consider them cheating. I usually ignore them, because if some piece of information isn't revealed during the course of the story, then it's not relevant to the plot and everyone can't be expected to know it. There are ways to let the rest know what powers your character has (like, using them), and ways to let the rest know the important parts of his personal history. I don't mean posting mini-biographies in the middle of a post... "and then our character remembered the day he was born..." or giving long scientific explanations at the middle of a fight, just be creative and make sure you tell us what we really need to know. Long biographies I despise as well: if it doesn't play into the plot or shape the way your character behaves, why do I need to know that he broke a leg playing Street Fighter in fifth grade?
That's it... I'm not telling the rest what to do, just saying what I'd be interested in doing, in case anyone else feels the same way.