Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
vdNote - Share noteworthy moments from YouTube videos.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
YouDict - YouTube dictionary to search words, expressions & names
Bigtent - BigTent is a web-based organization and communication portal for groups.
Summary Panda - Remove annoying 'blah blah blah' parts of YouTube videos.