Individual Eastercon committees will have their own ways of providing discussion areas for convention members and potential members ... these usually include LiveJournal, Facebook, Twitter, perhaps a Yahoo or Google Group, maybe some bulletin board software etc. These will be listed on the website for each Eastercon.
There are various main online discussions going on regarding running Eastercons on Facebook (IA), LiveJournal (IA) and Yahoo Groups (IA)
(You don't have to be a Yahoo member to use the YahooGroup)