NELSN are the North-East London Squatters Network, a group made up of people from different squats around Hackney, Tower Hamlets and around up that way.
One things the network does is provide an emergency phone tree that can be contacted in the event of dodgy landlords, or dodgier policemen, coming round to illegally evict you. The message will get passed on and in theory a whole bunch of people turn up to support you. It actually tends to work as well.
More recently the network has started hosting Practical Squatting Evenings twice a month, with a view to getting people together to open squats and to answer peoples squatting questions. There is also an empties list that it would be nice to get help keeping up-to-date.