Bookmark OS - Bookmark OS is like Mac or Windows optimized for bookmarks.
Siimpl Bookmarking - Start collecting and organizing what interests you
Bookmark It - Create awesome notes on YouTube videos
UnderlineMe - Highlight, bookmark & organize research from any site
Twitter Bookmarks - Create shortcuts to your favorite users/tweets on Twitter
Tixio - Work as a team without the clutter! Organize, optimize & coordinate.