Do social bookmarking in high page rank sites like
Delicious
technorati
reddit
slashdot
Digg
Diggo
stumbleupon

You can easily get lots of social bookmarking sites in Google. It is best if you can use do follow and different different IP social bookmarking sites.

There are many sites for Bookmarking:
1.http://www.bubblews.com
2.http://www.apsense.com/
3.http://tizags.com
4.http://www.justrage.com
5.http://ablynet.com
6.http://www.asrona.net
7.http://www.akonter.com

Below are some of the best social bookmarking sites:-

Folkd.com
Delicious.com
Digg.com
Diigo.com

Stumbleupon.com
delicious.com
digg.com
diggo.com
linkago.com
folkd.com
blinklist.com
reditt.com
youmob.com
sitejot.com

these are some of the famous sites for bookmarking..

Delicious, diggo, techdirt, reddit, stumbleupon.