Wayback Machine - Browse through over 150 billion web pages archived from 1996 to a few months ago.
Firefox Sync - Bring your Firefox bookmarks, tabs, or passwords wherever you go with Firefox Sync. Share between computers and mobile devices. Get Firefox now!
Archive.md - archive.is allows you to create a copy of a webpage that will always be up even if the original link is down
LinkLocker - LinkLocker is a lightweight bookmarking service with an emphasis on privacy.
FreezePage - FreezePage is a free service for taking online snapshots of web pages.
Linkman - Linkman Pro allows for managing large amount of URLs in its own database.