Lightning Talks are series of short strictly timed five minute talks each followed by two minutes for questions and answers during which the next speaker gets prepared (by e.g. disconnecting the previous speaker's laptop from the projector and connecting his own instead). The formula was used at ILC'2009 in sessions of 4 to 8 talks, and was a tremendous success.
Indeed you don't need to have that much to say to give a Lightning Talk, and so the formula lowers the barrier to entry and allows for a wider diversity of ideas to be presented at such events. At the same time, the strict constraint forces the speaker to be more concise, maybe even poetic, in conveying his ideas. Several participants remarked that since Lightning Talks were both so short and precisely timed, you could rehearse them many times before you gave them, making delivery more powerful. Additionally, some argued that the short duration limits the potential for either speaker humiliation or listener boredom, once again giving incentive for people to participate on both ends of the communication, promoting the exchange of ideas.
And so, I instituted such Lightning Talks at the Boston Lisp Meeting; so far, they have been well-received, and many people have subsequently volunteered to give one -- which makes me hopeful about their positive impact on the exchange of ideas within the community.