Wikis. They could be a way to go.

I used a Wikis to plan a trip with my daughter. She preferred (as well as I) to just pass a document back and forth by email.
In our branch, we've thought about setting up a wiki for different projects, but found that a document on the shared folder was easier to access by everyone.
I would use a Wiki, though--if others were willing. If the participants are all adept and willing to log in as often as necessary then it could certainly be an efficient way to go.