I heard about this via the nice people at Past Tense.
Hidden Histories: Common land and squatting in Hackney
A walking tour of central Hackney revealing the histories of common land use and squatting over the centuries.
Sunday 17 July 2pm
Meet at 2pm outside the Lido on London Fields.
The walk will last about 2 hours, followed by a picnic in London Fields
All welcome!
The Radical History of Hackney 
You could attend this one too beforehand if you want squatting to not just be history:
http://www.squattastic.blogspot.com/