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