1. get ONE person to Make decisions, also have a backup ready to step in, then a backup for the backup. Everyone knows the general "plan" for teh mod.
2.)A File Host like :http://www.4shared.com/login.jsp?sessionUnavailable=1
Keep it internal and you can make folders for all sections: models/maps, voices, missions ec t... Point is, any team member can access it and if one person goes away the files aren't lost (back them up!)
3.)Assign small bits and keep to deadlines, then update the status thingy MONTHLY.
Those sound liek solid suggestions.