What is Social bookmarking?
Social bookmarking is a method for Internet users to store, organize, search, and manage bookmarks of web pages on the Internet with the help of metadata.

How social bookmarking Work?
In a social bookmarking system, users save their blog or web site links to web pages that they want to remember and they share. These bookmarks are usually public, and can be saved privately, shared only with specified people or groups, shared only inside certain networks, or another combination of public and private domains. The allowed people can usually view these bookmarks chronologically, by category or tags, or via a search engine.

Social bookmarking site can help for SEO?
Yes if you post you data in social bookmarking site you can be found some more hits. Some social bookmarking site also helps you to gets some hits from Search Engine.

Here you can found some list of social bookmarking site.

Shake Now Beta
30daytags
BlinkBits
BlogHop
BlogLot
BlogMarks
BlogMemes
BlogPulse
BmAccess
browsr
Fark
CiteULike
clipclip
clipmarks
Complore
Connectedy
Connotea
de.lirio.us
del.icio.us
digg
diigo
fantacular
Feedmarker
Feed Me Links
Furl
Gibeo
GoKoDo
Google Notebook
IceRocket
Kaboodle
linkaGoGo
linkfilter.net
linkroll
Listible
Lookmarks
Mister-Wong.com
ma.gnolia
My Link Vault
Netvouz
Newsvine
Now Public
openBM
Pop URL’s
RawSugar
reddit
Rojo
Rollyo
Scuttle
Shadows
Shoutwire
Simpy
Sitetagger
Smarking
SpotBack
Spurl
StumbleUpon
taghop
TailRank
Ticklr
Uvouch
unalog
Webride
Yahoo My Web 2.0
yoonoo