The Green Drinks events have been a lot of fun and have really stimulated a lot of discussion around sustainability. Previous events have included speakers from various backgrounds including Poet (a major Ethanol producer in the US), the Plain Green Conference, Copenhagen Climate Change Conference attendees and a Mayor's forum.
Along with the speakers, the rest of the time is spent just meeting people who believe in sustainability. During this time, people can discuss projects that they are working on regarding green projects or ideas that they have and want some discussion on. The nice part about the events is that they are usually at a bar or restaurant, which gives the meetings a very laid back feel to them. This allows the people who show up to feel comfortable and not feel like it is some big event that they have to be tense or dress up for (even though a lot of them come straight from working, so they are in their business clothes).
They have also did a great job with their branding. They have had some great artists create posters for each meeting and each of them have been great, which a couple of them I have included on this post.
If you are in the Sioux Falls area, you should try to check it out. The communication on sustainability and green innovation, jobs, energy, etc. has been a great way to get a discussion started on those topics.