Every time you add a bookmark to one of your pages in one of these sites you create a backlink. If you bookmark every piece of content you create in all of these sites you can build a lot backlinks over time. For best results, you want to make sure that the bookmarking sites provide a real, do-follow link. There is much debate as to whether or not no-follow links are still useful so I wonít get into that here. However one thing you do want is a real link. Several sites donít provide real backlinks Ė they use their own form of dynamic link which does not count as a backlink.
One other thing to be aware of is that even though these are your personal bookmarks, you need to ensure that they are public Ė that way other people (Google really) can find them. But be careful, some bookmarking sites such as Connotea have a specific niche and probably wont appreciate your toenail clipping bookmarks.