ownCloud is a free and opensource file sync and share app which is self hosted.

StumbleUpon is a discovery engine that finds and recommends web content to its users.

Raindrop.io syncs bookmarks into the cloud and makes them beautiful as well as easy to search.

GC Bookmarks is a cloud based bookmark manager.

Speed dial is a replacement of new tab page with quick access to your most visited pages, bookmarks and browsing history.

Easily save interesting webpages to Google with the new Save to Google extension.

XMarks is a cloud based bookmark management platform.

Firefox Sync allows accessing your open tabs, bookmarks, history, passwords and preferences everywhere.

Fretsi is a social knowledge platform that makes everyone's knowledge public and rewardable.

lumio is an online content organizing platform.

Memotoo sync all your contacts from Gmail, Facebook, phone, Thunderbird, Outlook, etc in a single address book.