Da! is a co-operative of artists and musicians who "reclaim public commercial property" for the purposes of putting on art exhibitions. Basically they're squatters who squat in commercial properties in London and throw open their doors to the public to anyone interested in their left field Artworks.
I love the philosophy behind it - their fuck the system attitude, and greatly respect their balls for doing just that. What they're doing is legal, it's protected by Squatters rights, so long as they don't force their way into the property or damage anything whilst they are there.
As part of their "Art" they've reclaimed shop spaces, pubs and come up against all kinds of hired heavies working for the corporate bad guys who have illegally and forcibly tried to eject them from the properties (that is without obtaining the legal paperwork).
Most recently they've reclaimed the old Iraqi embassy in London and are throwing the doors open on Thursday night at 9pm for an exhibition of their wares. In my opinion i think the philosophy is greater than their art, but they are undeniably an interesting group of people.
http://www.kafiyeland.net/DASITE/HOTELDA/index.html