We use Meetup as the main place to get details about Meetups well in advance, but also post our meetups on Facebook and Twitter a week or so in advance. If it looks like a meetup is going to be lightly attended, that's usually because most people have RSVP'd on Facebook - we check both! Join us there for online discussion. https://www.facebook.com/groups/138477179510747/
We are a social organization dedicated to education and the promotion of critical thinking, science and skepticism. Our meetups generally consist of a twenty minute presentation and then group discussion, but we also occasionally have speakers.