Most of social bookmarking sites have the following steps:
1- Register an account.
2- Suggest a URL
3- Get bookmarked, (digged...)
Below a list of the most popular as per OnlyWire:
Ask
Bebo
Bibsonomy
Blinklist
BookmarkSync
Connotea
Delicious
Digg
Diigo
Facebook
Fark
Faves
FriendFeed
Google Bookmarks
Hi5
Jumptags
LinkaGoGo
Mister Wong
Mixx
Multiply
MySpace
Newsvine
Plaxo
Plurk
Propeller
Reddit
Simpy
Slashdot
Spurl
Stumbleupon
Tumblr
Twitter
Yahoo Bookmarks
