Here are some links to people or organisations that you might find useful:
General
http://www.transitiontowns.org/
http://www.selfsufficientish.com/
(A brilliant little film to make EVERYONE watch):
http://www.storyofstuff.com/
http://pangeaday.org/
http://coinet.org.uk/
http://www.resurgence.org/
http://www.ted.com/index.php
http://makezine.com/
Food
http://www.getgrowing.org.uk/
http://www.btinternet.com/~grow.communities/
(lots of information on this site, local fruit and veg box schemes, farmer’s market, …)
http://www.gardenorganic.org.uk/
http://www.allotment.org.uk/
http://www.allotments4all.co.uk/
http://www.britishbee.org.uk/
Trade and swaps
http://www.fairtrade.org.uk/
http://www.traidcraft.co.uk/
http://www.freecycle.org/group/United%20Kingdom/London/Hackney
Energy
http://www.energysavingtrust.org.uk/
http://www.ecotricity.co.uk/
http://www.goodenergy.co.uk/
http://www.joju.co.uk/
http://www.heatproject.co.uk/
http://reuk.co.uk/
Transport
Cycling:
http://www.hackney-cyclists.org.uk/
http://www.hackney.gov.uk/es-cycle-training-faq-547.htm
http://www.tfl.gov.uk/roadusers/cycling/8966.aspx
Train travel:
http://www.seat61.com/
http://www.nationalrail.co.uk/
http://www.eurostar.com/
Car-share schemes:
https://www.liftshare.com/uk/
http://www.shareacar.com/
http://www.nationalcarshare.co.uk/
Walks:
http://hoop.ground-level.org/
Children
http://www.thenappylady.co.uk/
http://www.tattybumpkin.com/
Media
http://www.adbusters.org/
Natural burials
http://www.greenendings.co.uk/
http://www.nativewoodland.co.uk/