http://www.aspirationtech.org/events/devsummit

This should be of interest to anyone involved in both Wikimedia Foundation issues and open source technology. Sorry for the late notice, I just found out about it. Aspiration has a couple of other cool projects, such as their index of nonprofit tools (some of them open source, some of them not):

http://www.socialsourcecommons.org/

As well as Penguin Days:

http://www.penguinday.org/