It's called Minu Eesti--My Estonia, as in your Estonia--and it's happening on May first all across Estonia. One hundred thousand people, both Estonians and foreigners, will come together for countrywide brainstorming sessions on how to make Estonia a better country. The mõttetalgud (mõtte means "thought" and talgud are like a Mennonite house-raising) are organized by the same people who organized the cleanup of 10,000 tons of trash by 50,000 volunteers this time last year.
If you'd like to take part, write Ms. Liina Parve and tell her you'd like to join an English-language group (firstname.lastname@example.org). Some Estonians are of course needed in the English groups.
Here's American (and Elva, Estonia, resident) Robert Oetjen's bit to promote the event: