Plugin/service suggestion for conference attendees communication

A client of mine is organizing a conference and is looking for a way to allow attendees to communicate easily in one place. Things like available seats, extra space in accommodations, looking for recommendations for local restaurants/activities, etc.

There has been a suggestion to add a wiki but the info is so temporary and one-off that it seems like a less complex tool could better serve the purpose.

I was thinking embedding a Twitter feed for a specific hashtag might do the trick but I’m hoping someone might have an idea of a plugin for their WP site or even some other third-party service.