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.
LinkLocker - LinkLocker is a lightweight bookmarking service with an emphasis on privacy.
SaidIt.net - Saidit.net - say your truth.
Diigo - Diigo is a powerful research tool and a knowledge-sharing community
Tildes - A non-profit community site driven by its users' interests
Linkman - Linkman Pro allows for managing large amount of URLs in its own database.