OS X Application for Scraping HTML of a Set of Tweets
Storify.com is a pretty cool way to curate something like the Tweetup you mention.  It lets you search for tweets (or other social media) and stream it into a list of points to make up your story.

I first noticed Jason Kottke using it a couple of days ago to make a story out of the tweets from Gavin Purcell about production of that night's Jimmy Fallon show.   I have been fascinated by it ever since.