Reddit - Reddit gives you the best of the internet in one place. Get a constantly updating feed of breaking news, fun stories, pics, memes, and videos just for you.
Pinboard - Pinboard is a personal archive for things you find online and don't want to forget.
SaidIt.net - Saidit.net - say your truth.
IsYourLinkSad? - Is Your Link Sad. Make It Happy. Share your URLs to people who actually care.
Tildes - A non-profit community site driven by its users' interests
The Bored Hoard - Sieve the web for cool websites you probably never knew existed. Supporting the smaller independent sites that Google ignores. All revealed in a weekly box delivered online every Friday.