I organize Hackers and Founders Indianapolis. Our most recent meetup had 40 people.
Like @iamelgringo said, I don't post our meetups to Hacker News because the post falls off the page immediately. I know there is a community of Hacker News people in Indiana who aren't connected but would be if there was a way on Hacker News to see when others are gathering for a meetup in their area. i.e. an events listing.
Other than that, meetup.com really serves all of our other meetup organizing needs.