fferraiu

This plugin allows you to integrate your wordpress blog with the platform capabilities of meetup. 
This provides a widget that allows you to view a list of recent activities of your group meetup.

MeetupUserActivityWidget

Allows you to integrate your wordpress blog with the platform capabilities of meetup

Rick Radko

A simple widget for use with a <a href="http://meetup.com" rel="nofollow ugc">Meetup.com</a> group. The plugin adds a widget that shows a link to your Meetup group.
Simply enter your Meetup group name and it’s URL and save. You can display the widget with or without a title.
Support
Support for this plugin is limited to fixing confirmed bugs and improving the plugin with enhancements that can be reasonably accommodated.

R3DF Meetup Widget

A simple widget for displaying a link to a meetup.com group.

MeetupUserActivityWidget vs R3DF Meetup Widget