Not Put My Groups "Below The Fold"
As a meeting organizer, when I log into Meetup.com, chances are I'm going to administer my meetings.
However, the home page I'm presented with after login is filled with news and other Meetups around town, putting the one thing I'm interested in "below the fold." Having to scroll down to get to what I'm there for 99% of the time is not good user interface design.
When a meeting organizer logs in, I recommend his Meetups be featured prominently near the top of the page.