More groups of people who want to fiddle with opensource software: Hackaton.se. They have an event in Malmö, at a school, 23-25 november.
Just to let you know, so you can spread the word. I’ll write more when I know more.
Update! An attentive reader, also being the organizer of the upcoming event emailed me, and told me more. It’s called “Hack-a-ton”, note the Scandinavian spelling. URL changed to reflect this.