For DDD4 we are organising Grok Talk and Park Bench lunch time activities. These are your chance to participate in the day. And for the best grok talk on the day we are offering a MSDN subscription.
The Grok Talks are open to anyone who is already registered for the day (we are full on registrations) and a wiki has been setup where people can put down their name and the talk http://www.thehughpage.com/DDD4LunchTime. A Grok Talk is a 10 minute deep dive on a single feature of an API or Tool. There are great examples here. As such it is much less of a challenge than a full presentation. All you need is a USB stick with your presentation on it (though let us know via the wiki if you expect any software to be installed, and provide some contact details).