Xmarks Firefox Plugin

Xmarks, a very useful firefox addon that enriches your search engine experience. This service compares the searched result with data on their server and recommends sites that have been frequently bookmarked and search for similar sites in a click. It keeps your bookmarks safely backed up and in sync and you can use it on different computer on which xmarks is installed.

https://addons.mozilla.org/en-US/firefox/addon/2410