Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Bucketlist.org - Log and catalog all the stuff you want to accomplish before you expire.
Event Hunt - Startups and Tech Events Curated By Locals
List Challenges - Earn points for your life experiences. Find lists that interest you, and mark off what you've done.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Life Listr - ***AS FEATURED BY APPLE***