Patagonia's Tools for Grassroots Activists Conference.  It's held every 18 months, so look for the next about a year from now.

Back in 1994, we organized our first Tools for Grassroots Activists Conference. We invited a handful of seasoned activists to help us train members of some of the environmental groups we support. We asked them to share their experiences and their knowledge to help our grantees become more effective advocates for the natural world.
The tools environmental activists need to attract members, publicize issues, communicate to donors and inspire citizens to take action are, in essence, very similar to those we use every day at Patagonia to sell clothing and gear. To be effective in today’s fast-paced, technology-charged, competitive world, we need to develop strategies, clarify our messages and find useful and affordable methods of advertising. One can’t be effective without the right tools in one’s toolbox.
Patagonia covered all conference expenses – training, lodging and meals – and asked participants to bring their stories, passion and ideas. Those who attended this first conference appreciated the training so much, we have repeated the event every 18 months since. To date, more than 800 activists have joined us.