Delicious: export your bookmark data and setup your own Drupal userlinks server
Other free bookmarking services are available, and you can export your bookmarks from delicious.
Shame yahoo missed a trick with this. the bookmarks users tagged in delicious could have been used to provide targeted advertising on subjects with those tags, yet delicious is ad-free perhaps to the pleasure of some,.
The stackexchange family of websites, and goodle themselves seem to get it done right with well positioned non-imposing adverts.
The other trick is the user voted search potential, as opposed to machine generate search results. The side effect of delicious as a social bookmarking tool is that searching within it always produces results selected by people, popularity is automatic by the amount a result is linked by its users, rather than a more vague rating system.
digg, stumbleupon, offer alternative delicious.
Otherwise you might want to do a diaspora style approach and host your bookmarks yourself, with cheap shared web hosting and free Drupal and the userlinks module this would largely provide delicious functionality. Then federate your machine with other people doing the same and you have the social, bookmark sharing element.