What methods and/or media have you employed to help your designers work together throughout the development process?

Wikis! I can't oversell how useful our wikis are for development. We use them for organizing everything from organizing meets to keeping track of building projects to group design projects, etc. Highly recommended and far better than passing Word documents back and forth if there are more than 2 people working on something.
--matt

We have an good old fashioned bbs on our server that we use as a forum for discussing our development. We do have a php forum system as well, but that is being worked on to be smoothly integrated with the mud characters before we start using them.

Private message boards mainly, although I've been checking out a few WIKIs lately as I'm sure that's the next logical step. We also use email and most importantly I regularly call and spend an hour or so talking to my fellow coder as we bounce ideas back and forth.

I've always done it that all designers must liase through a departmental head. The departmental head is responsbile for keeping track of everyones progress and informing any staff on any jobs, changes, or quirks that have occured. This is hard to pull off without someone dedicated, but it can work very very well.

We have several systems in place for redundency so that people have
some flexibility while still informing the rest of the staff and playerbase.

1. Mailing Lists
2. Discussion Boards
3. In-Game Note Boards
4. Dynamic Websites
5. In-Game Meetings (attempts made for weekly)

We also cycle input in for player suggestions through an in-game
command we all probably know...idea/bug/typo.  This is then weekly
evaluated by a staff member based on merit and if agreed upon, it
is added to a list of ideas slated for implementation.  The list is updated
using SQL to a website for review by anybody willing to look.

Over the years we've found that communication is the biggest problem
in development as well as in player relations.  Designers can't simply
communicate to each other but they need to inform players via notes,
helps, emails, etc. else feel the resentment of too many surprises.

Wiki.

We use an open-source program we found called phpCollab. Its a web-based, php and mysql driven Collaboration application suite. Its got a main and subproject message board system, file upload capabilities, project lifecycle, etc.

Website:

-- Michael