I don’t know if you already know this or not but you can set up your own social bookmarking website for free by using Pligg CMS Solutions!
About a year ago, I started a Turkish website called Linkopedi where I was intending to give links for social bookmarking websites and easing link building process for my visitors. After some time, I saw my users were eager to send their website data and asking me to publish them on this website. As a very curious person, I really love experimenting new things so I said why not and added a directory folder under my website and started building links for my visitors; it was very risky I accept but at the end of the day my visitors were happy and it was increasing my traffic as well.

Social bookmarking is another time intensive method while doing ethical link building yet it is unavoidable. Below is a list of useful sites to ease your social bookmarking works. Please let me know if you have any suggestions.