The biggest problem with social bookmarking is those sites you see today won't be found tomorrow. Also these scuttle sites and pligg.com sites are not really bookmarking sites. Well there are some but more are just domain reseller setup these scripts so their domains would gain some backlinks. After couple of months they would remove bookmarking script add new layout and site and they put it on sale.
So here are some real social bookmarking sites. Each of these sites are different and you will to find how u put your links in and how to make those public. But it's worth trying because these are real sites.
Code:http://www.stumbleupon.com/ http://delicious.com/ http://www.newsmeback.com/ http://blinklist.com/ http://www.folkd.com/ http://www.reddit.com/ http://friendfeed.com/ http://slashdot.org/ http://www.newsvine.com http://www.spinsnap.com/ http://fichey.com/ http://www.suggy.com/ https://www.google.com/bookmarks/ (not public anymore ?) http://www.theneeds.com/ https://gimmebar.com/ http://www.bookmark.com/ http://www.bookmarks.io/ http://www.skloog.com/ http://yummymarks.com/ http://zootool.com/