Kelly Choyce-Dwan

For use with a <a href="http://meetup.com" rel="nofollow ugc">Meetup.com</a> group.
This plugin creates two widgets: one a list of events from a meetup group (by ID or URL name, for multiple groups use IDs); the other shows details about single event (by ID) with a link to RSVP – using OAuth if keys are specified, otherwise just a link to the event on meetup.com. Does require at least an API key (which it asks for on the settings page).

Meetup Widgets

Adds widgets displaying information from a meetup.com group.

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.

Meetup Widgets vs R3DF Meetup Widget