Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Co-op - Find interesting things to do with like-minded people
Facebook Local - Discover places to go and events happening near you
Activities Mapper - Find things to do, eat, and drink near you in London
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Interests - Explore your interests