Twitter has been used successfully at various conferences to connect delegates before, during, and after the events. It's a "micro-blogging" service that allows users to post brief updates via SMS, IM, the web, or desktop software. You can read updates of others in the same ways you post updates.
I've set up a Twitter account for Handheld Learning 2007 at
http://twitter.com/hhl. An aggregation of updates from everyone participating in the conference "Twitter-fest" can be read at
http://twitter.com/hhl/with_friends.
Because Twitter can be accessed in so many ways, it's perfect for conference-goers who may be using a laptop, handheld, or mobile phone. It takes a while for most users to actually understand the potential value of connecting by Twitter. I suggest using it for a week or more before judging its usefulness.
I've written a one-page PDF file to help delegates set up and use Twitter. Please review the PDF and make suggestions for improvement:
http://learninginhand.com/notes/Twitter_HHL.pdfI look forward to seeing your 140 characters (or less) updates on Twitter!