I'd say people should add their name, a proposed talk title, short description and a presentation length to the wiki. Far easier to keep track of all the proposals that way than having to trawl through either a mailing list or the forum.

I should add that once we know what sorts of talks people want to do, it should be easier to plan the structure of the day, numbers of talks, sessions (depending on the number of topics and how they could be streamed), etc.