With all the great online resources for progressing the open government movement it's important to remember the offline element and the tools we can leverage to organize, promote and host events.
Depending on who you're targeting, some tools may be a better fit than others, though you should be willing to explore a few platforms to see what your audience will respond to best. You'll also find it useful to list your events on multiple services if you want to attract the largest amount of people and know there's little network overlap.
Two of my favorite platforms for organizing events are Facebook Fan Pages and Meetup. Though slightly different from each other, they have similar features that makes it simple to invite and engage participants. Both have discussion boards, photos, polls and ways to contact group members. While Meetup as a platform is built entirely with events in mind and has additional features you won't find on Facebook, the sheer size of Facebook is clearly an advantage in connecting with people.
Eventbrite is another popular service with a number of features to help you publish, promote and manage events beyond what's available on most sites. If your event requires ticketing, waiting lists, badges or various pricing levels, you might want to check out this service.
For general event broadcasting with less of a feature set, you can post your events to Upcoming.org, LinkedIn and Eventful. Pro tip: For maximum efficiency, create your original event URL on either Meetup, Facebook or Eventbrite, but link to it from these general broadcasting services. Other similar, notable services include Zvents, Plancast and Google Calendars.
These are just a handful of the services you can use. The main thing you should learn is to look for a service that provides you with the tools you need and to use that service in combination with broadcasting platforms to reach your core audience. What do you think? What services have you used in the past?