Flinkin.com - a social bookmarking site where links can be stored into folders using a bookmarklet. link titles can't be edited. decent.

markme.me - a social bookmarking site. a basic bookmarklet dumps pages into your own page.

Folkd.com - social bookmarking site with an average add-on. every link added to the site requires typing in a Captcha without Pro account.

Addthis.com - Now has a add-on for Firefox; It however only shares with one service that I've added a Stickr to so far.

SecondBrain.com - Social bookmarking site. Decent bookmarklet. Can organize websites into collections with an automatic screenshot.