The first is the DO Lectures, which take place in West Wales, UK. A colleague recently mentioned this conference that is all about making change happen... it appears to be a variation of the TED Conference (Technology Education Design). Like TED, DO has lectures available online. As the DO website points out: "The idea is a simple one. That people who Do things, can inspire the rest of us to go and Do things too. So each year, we invite a set of people down here to come and tell us what they Do." I have not attended DO, but would like to hear from others that have...
The second is the Living Future (the un-conference for deep green professionals) put on by the Cascadia Chapter of the US Green Building Council. (It's happening this coming May in Seattle, Washington). I attended Living Future last year in Portland, Oregon and really enjoyed the way there were so many opportunities to connect with the attendees (gathering was limited to about 500 attendees).
These un-conferences are breaking the mold on how we share ideas with groups-- including having great talks available online.
Check them out!