Talks are a really good idea!
In vancouver, we have been explicitly doing math skillshares for a few meetups. I've also been planning math talks for the local hackerspace. People seem to like math once you get it out of a "this will be on the midterm" context. I'll go ahead and recommend math talks.
One thing that I'd like to see at the next megameetup is a few informal focused discussions on various topics related to the community, like meditation or diet.
People should prepare for them, but I don't think that say, powerpoints would be necessary. Just trying to encourage knowledge transfer.
Anyone on the East Coast interested in giving one? Any things you'd like to see?
Schedule Update: The Megameetup will be held on on the weekend of January 27th or February 4th.