Bookmark It - Create awesome notes on YouTube videos
Bookmark OS - Bookmark OS is like Mac or Windows optimized for bookmarks.
POAP - POAP is a new way of keeping a reliable record of life experiences.
PageMarker - Save, organize, annotate and revisit your bookmarks
Twitter Bookmarks - Create shortcuts to your favorite users/tweets on Twitter
Pastel Bookmarklet - Mark up any website from your browser, for free