TodaysMeet. This is a funky little resource, pulling tweets with a specified hashtag into a room, while at the same time allowing people to join the room and communicate directly in the room, but without the requirement for a Twitter account. The advantages of this situation are that your audience may not be on Twitter, but they can simply join a room you create on the fly, you prefer private discussions, and you just want to pull in stuff from Twitter that's appropriate.
It looks like a really nice resource.